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Many games provide secret levels that aren't necessary to finish them. Sometimes they are based around gimmicks or themes that aren't in the "actual" game. Sometimes they are much more difficult than the main game's and are essentially a secret challenge, or they feel like they could fit right in the game but the devs couldn't find an exact place to put them in the normal progression (and making them secret was better than leaving them out or dummying them). Will also be necessary for 100% Completion.

The reward for finishing a Secret Level can range from a helpful item, a shortcut, a secret trinket, some information regarding the story, a full-blown revelation that changes how the plot is interpreted, a boatload of points, or a pat on the back.

See Minus World for such levels that only exist due to glitches, or Dummied Out if the level was purposely designed but not meant to be accessible (Not that this stops people sometimes, thanks to Good Bad Bugs or modifications). Also see Bonus Dungeon, which is a mostly equivalent trope (the usual main differences being what genre they're found in, how much the game hints towards their existence, and whether you find them mainly by searching every nook and cranny or setting off enough Event Flags).


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  • Bubble Bobble, NES (and thus Virtual Console) version has a secret path that the players must take to get the best ending. It wasn't there in the arcades.
  • The Legend of Zelda: Spirit Tracks: Some of the playable locations can only be unlocked by restoring rails with Force Gems that are rewarded by completing very obscure and/or difficult sidequests. Examples include the Snowdrift and Slippery Stations in the Snow Realm, and the Lost at Sea Station in the Ocean Realm.
  • Toe Jam And Earl has one of the most puzzling floors in the game: Floor 0. How do you get to it? By swimming to a far, far away island in the 1st level of the game. Guide Dang It!!
  • Tomb Raider:
    • Tomb Raider III has a secret level accessed by finding every (well, technically, all but one, due to an oversight) secret. It appears to have been intended to be a normal level (and showed up in various previews of the game) at first but was cut for some sort of progression reason.
    • The Tomb Raider II Gaiden Game Golden mask also has a (very wacky) secret level accessed by finding all the secrets in the previous levels.
    • Tomb Raider: Anniversary has the "style units" gained after finding most of the secrets. Not really a level, as it is just an explorable visual demonstration, but it shows off various experimentations with the art-style of the game and locations.

    Action Game 
  • Rolling Thunder 3 for the Genesis has Rounds A-C (one of them being a Nostalgia Level) that serves to substitute the two vehicle stages (Round 3 and 6), as well as the Hijack stage (Round 9), while keeping all of their current weapons and ammo.
  • Syphon Filter: The Omega Strain's secret missions are unlocked by completing each block of missions within par time with all of the objectives accomplished.

    Beat 'em Up 
  • Jackie Chan Stuntmaster have a secret Shaolin Temple stage that Jackie can access by collecting all the Golden Dragon Heads. He even gets his Drunken Master training uniform for said level, and players with a saved file can replay the whole game with this new outfit.

    First-Person Shooter 
  • The Blood Game Mod Death Wish for Blood, which places great emphasis on making level transitions logical, puts a spin on this — each secret level is followed by revisiting a fragment of the previous map, where the player has to face a single tough fight (usually a boss and his flunkies) before he can head to the regular exit to resume normal level progression.
  • Descent has some secret levels late in the game. They are difficult, but you can be rewarded with a lot of points and some weapons upgrades.
  • Doom:
    • Each Episode in Ultimate Doom has a secret map that are accessible via a secret exit in one of the Episode's maps:
      • Episode 1 has Military Base, which is accessible via a secret exit in Toxin Refinery. It is a conventional map, just being a bit more difficult than other Episode 1 maps, but it does notably contain the first teleporting monster ambush in the game, though this trap was replaced with a normal Monster Closet ambush in all of the '90s console ports.
      • Episode 2 has Fortess of Mystery, which is accessible via a secret exit in Command Center, though its accessibility varies in early console ports; in the Super Nintendo port the secret exit to it was moved to Refinery, in the Playstation and Saturn ports the secret exit to it was moved to Spawning Vats, and it wasn't a secret map in the Jaguar, 32X, and GBA ports, instead being the final map of those ports. As for the map itself, it's notorious for its overt simplicity, consisting of just two plain rooms, one with four Barons, and the other with ten Cacodemons, with its purpose being to show off monster infighting.
      • Episode 3 has Warrens, which is accessible via a secret exit in Mount Erebus, though the map was removed in the Jaguar, 32X, GBA, Playstation, and Saturn ports (but interestingly it was retained in the SNES port). This map has the gimmick that it initially appears the player was sent back to the Episode's first map, Hell Keep, being exactly the same as that map up until the secret near the end, which no longer has a Rocket Launcher, the first signal that something isn't right. Then when the player steps onto the "exit" teleporter, the walls come down to reveal a large arena with a Cyberdemon, and then the player must backtrack through the map, with more rooms opened up containing more dangerous enemy encounters than the original map had.
      • Episode 4 has Fear, which is accessible via a secret exit in Perfect Hatred, though the map was removed in the Playstation and Saturn ports, and of course doesn't exist in the other console ports that don't have Episode 4 (the SNES, 32X, Jaguar, and GBA ports). It's a banal conventional map that is noticeably much easier than the two Episode 4 maps precededing it, with its only noteworthy feature being its symmetrical design.
    • The Playstation and Saturn ports had a few of their own exclusive secret maps that were never seen in the PC version nor any of the other ports:
      • In the Ultimate Doom portion of these ports, there's a new secret map called The Marshes, which is accessible via a secret exit in Twlight Descends, which itself is a new map exclusive to these ports. This map is a large arena resembling, as the name implies, a marsh-like area, containing a Cyberdemon and a handful of other mooks.
      • In the Doom 2 portion of these ports, the two secret Wolfenstein maps were replaced by two new secret maps:
      • The first such secret map is The Mansion, accessible via a secret exit in Suburbs. It is mostly a conventional map with nothing out-of-the-ordinary gameplay-wise other than a tricky teleporter maze puzzle, but the map does visually standout for its depiction of a Resident Evil-like mansion, taking strong advantage of the ports' colored lighting to create an unsettling atmosphere, with it especially standing out compared to the drab Doom 2 maps.
      • The second such secret map is Club Doom, accessible via a secret exit in The Mansion. The map starts out looking unsettling, being a pitch-black area only lit by a row of candles going into an ominous looking building. But upon entering the building and turning the corner, loud rave music starts playing as the player enters a strobelit nightclub area full of Revenants on a dance floor and in go-go cages.
    • The original Xbox port, while otherwise mostly a 1:1 port of the PC original, has its own unique secret map in Episode 1: Sewers, accessible via a secret exit in Hangar. This map was one created by one of the ports' developers, David Calvin, back in 1994, otherwise there's nothing noteworthy about it other than being a banal 1994 WAD that really shows it age. This map was not included in any other port, but is available as a standalone WAD online if one wishes to play it. Interestingly it was also available several years earlier in Maximum Doom, an official WAD compilation from 1995 that contained nearly 2000 WADs downloaded from the internet, as well as being included in the many other unofficial shovelware WAD compilations of the '90s.
    • Doom II has two secret levels set in levels taken from Wolfenstein 3-D, with one accessed from a secret exit found in the other. The second one requires you to kill four clones of Commander Keen hanging from a noose to access the exit.
    • Doom 64:
      • The three standard secret levels in the main campaign provide tangible rewards found nowhere else. Each gives one of three Demon Keys to power up your Unmaker weapon, provided you solve a puzzle in each level. You can also find significant perks, such as an Unmaker as early as the first act of the game. Each Demon Key also reduces the difficulty of the final level significantly by allowing you to close one demon portal per key.
      • A super secret level called Hectic, accessible by reaching the secret exit of the first normal level, doubles as a Brutal Bonus Level for featuring traps that are extremely difficult to overcome. But if the player prevails, they will unlock a set of features like accessing hidden levels that are unavailable otherwise.
  • GoldenEye (1997): The Aztec and Egyptian levels. The former deals with the Drax Corporation from Moonraker, and the latter has Baron Samedi, who somehow procured the Golden Gun and is taunting MI6 with it (that level doesn't make a whole lot of sense story-wise, come to think about it). The levels carry their own unique challenges: the Drax soldiers have an over-reliance on grenades which sharp-shooting players can turn against them, and the Egyptian tomb has a Guide Dang It! method of getting the Golden Gun.
  • Halo 2 has the multiplayer map "Foundation", which is a remake of "Thunderdome" from Marathon 2: Durandal, and is only unlockable by following some rather specific criteria in the final single-player level. Behind the scenes, "Foundation" was a map designer's unofficial side-project, deemed not up to the quality standards of other maps but interesting and fun enough to add to the game, so this unlockable map system was the compromise made. Unfortunately, the unlock method was so obscure and glitchy to boot that Bungie just made it unlocked for everybody in a patch.
  • Marathon Infinity: Blood Tides of Lh'owon has several of these, which are either alternate endings where the W'rkncacnter destroy the universe, or "co-op carnage break" levels that can (or are supposed to) only be accessed in multiplayer mode. Then there's the three Vidmaster's Challenge levels, found via a secret exit on the final stage. The best-hidden secret level is "Hats off to Eight Nineteen," which can only be reached by noting down strings of hex code found on terminals in the first and last levels, copying them into a text file and unzipping the file twice, whereupon it turns into a map file you can load in the game.
  • The "Panzerknacker Unleashed" missions in Medal of Honor Underground. They are based on multiplayer maps from the previous game, and they are very, very hard.
  • Level 4-0 in Medal of Honor: Allied Assault is accessible only through the console, and looks like it was supposed to be part of Mission 3, but was Dummied Out for progression/pacing reasons. There's also the Bazooka-Med bonus level accessed by earning the medal on Sniper's Last Stand.
  • Nitemare 3D goes straight from level 4 to level 6 if you play it normally. Or, you can simply push a bunch of boxes in front of one of a pair of dumbwaiters (which will otherwise just transport you back and forth) and get in the other to jump to level 5, which is full of gun-wielding human enemies.
  • The secret levels in Perfect Dark are retreads of previous levels from a different point of view, which reveal different parts of the story. The first one shows how an alien Mook kidnapped the CEO of dataDyne (she was later killed aboard the ship) and imploded the building, effectively destroying the company. The other two missions let you play as the grey aliens, one where Elvis alerts the Institute of being captured by Area 51 and you play through the entire level with diminished health, and the other has you play as a soldier among a platoon who landed on the planet after Joanna dropped the shields. Both missions are insanely difficult.
  • Quake 2 has three secret levels. The first - Lost Station - has noticeably more enemies than usual, but doing it will reward the player with an early Super Shotgun. The second - Sudden Death - is an interesting one: upon entering, you have 30 seconds to grab as much stuff as you can, then you're thrown back to the previous level and can't enter again; and its entrance is an innocuous waterfall in plain sight but can only accessed via a Rocket Jump. The third - Comm Satellite - is set on a space station accessible via a hidden teleporter and as such, has low gravity and only flying enemies.
  • Rise of the Triad: There's a secret level in each episode; locating them not only requires deep exploration, but also careful attention (since the exits leading to them are no different from those taking you to the next regular levels).
  • Serious Sam: The First Encounter:
    • The game has two secret levels: "Moon Mountains" and "Sacred Yards", reached by finding alternate exits in "Valley of the Kings" and "Luxor" respectively. The former is a detour through the source of the Nile and a break from the sandy deserts and canyons of Egypt. The latter is a Gimmick Level where enemies are hidden in every single destructible object, placed right before the final level of the game.
    • The Serious Sam Classics: Revolution release added an exclusive campaign called Bright Island, which has two secret levels of its own: "Valley of Wheat" and "Tropical Bluffs". The former explores the place where the former Sirian inhabitants of the island grew their food, while the latter is yet another Gimmick Level where all of the enemies have additional status effects.
  • Wolfenstein 3-D has one secret level in each episode (two in Spear of Destiny). Of note is the one from Episode 3: It's a gigantic maze where you collect bonus orbs for high score where you're beset upon by four ghosts. Four giant colourful ghosts. With googly eyes. Yes. It's a level of Pac-Man.

    Hack & Slash 
  • The secret Cow Level in Diablo II , which was made after various rumours about one in the original Diablo.
  • Diablo III has Whimsyshire, a land that seems ripped straight from Care Bears with smiling clouds, purple bears and unicorns. It can only be accessesd by completing a recipe, or killing a Rainbow Goblin. A later patch also added Greed's Domain, which is a rare portal that opens after killing Treasure Goblins. It features a unique boss and has pots that literally drop millions of gold pieces. Being lucky enough to enter one pretty much ensures you'll never have to worry about money ever again.

  • Entering a cheat code in Last Gladiator gives access to a secret "Victors" table.

    Platform Games 
  • Legend of Grey Moon has a number of well-hidden secret rooms; these are typically much easier than the rooms that make up normal areas, if not totally harmless, and most of the time are either silly jokes or completely meaningless. Particularly interesting are one level made of Epileptic Flashing Lights which is reached through a secret passage in another secret room, another containing a secret seventeenth gem, and the Special Thanks To room, a Developer's Room of sorts.
  • In the Nintendo video game adaptation of Attack of the Killer Tomatoes!, there is a bonus level if you sit through the end credits.
  • Commander Keen:
    • Episode I has a secret level which can only be accessed by going down a tricky side passage in another level.
    • Episode IV has one where you collect 12 Inch Worms to make a giant foot which then launches you to a secret temple.
    • Episode V has a secret level accessible by clearing the penultimate mandatory level via an alternate route you can enter through a well-hidden entrance near the regular exit.
    • Episodes III and VI have each one secret level accessed from the overworld map. You have to catch a friendly monster (in the former) or a hovering vehicle (in the latter) so Billy is taken slowly to a distant section of the map that is impossible to see from anywhere else.
  • Crash Bandicoot has several of these:
    • The first game contains two levels that need you to get keys from the Cortex Bonus stages to be unlocked.
    • Crash Bandicoot 2: Cortex Strikes Back has levels hidden within levels. Some of these are considered parts of the main level where you really need to know what you're doing to find them:
      • There's the hidden area within the Unbearable level, where you need to jump into a seemingly bottomless pit in order to gain access to a hidden area within the level, which swaps the level theme from a towards the screen chase sequence to a side scrolling section.
      • In the Bee-Having level, the player has to jump on what looks like a conspicuously static stack of Nitro crates to teleport to a secret section and get the purple gem.
      • There are the levels which you need to unlock by finding secret bonuses in other levels, such as standing on a hard-to-reach platform, or jumping over a long hole to get back to the polar bear, in order to unlock hidden levels, and alternate paths in other levels.
    • Crash Bandicoot 3: Warped does the same once again in accessing hidden levels with alternate routes, but makes you beat time trials to get to them. However, there are still two hidden levels not at all required for 100% completion, but required for 105% completion. While all of the secret levels in Crash 2 can be found without a guide with enough persistence, Crash 3's secret levels are really obscure. One of them has you driving into a sign on the side of the road in a motorcycle level (the only hint that it holds something suspicious is that its icon is that of an alien face).
  • Demon's Crest really has no mandatory levels after the very first stage, but the final two need to be unlocked on the world map by jumping into a cyclone in Stage 4.
  • Donkey Kong Country 2: Diddy's Kong Quest and DKC3 have a "secret" world that allows access to a better ending, and certain items you collect are focused around gaining access to these levels.
  • Eversion's secret level is unlocked after collecting all 240 gems in the game, and is necessary to get the good ending.
  • World 8, Sky Roost in HarmoKnight, which is unlocked after collecting 5 Tori Birds, is an entire Secret Level merged into one big world. It tries to mimick the earlier worlds, but (as the princess says) puts a twist on them. These eight levels look like normal levels, but then you enter one of the levels, and see thousands of Mooks, Spikes of Doom, and Bottomless Pits. You get the sudden realization that the princess told you these levels are Nintendo Hard. Final Trial is just simply a gigantic death trap.
  • Iji has Deep Sector, featuring a fun little battle against seven Assassins. Considering the most you ever have to deal with at one time other than that is one....
  • Kid Chameleon has many levels named "Elsewhere". All of them are technically secret levels. Early on, they generally have to be discovered and act as shortcuts, but later in the game, there are plenty that can accidentally be accessed and lead backwards (or just through to a different path of levels).
  • Super Meat Boy has regular secret levels which qualify as bonuses (required for 100% Completion), and then has intentional "Minus World" levels, which are just plain sadistic.
  • Mega Man:
    • In Mega Man X3, there's a secret level that can only be accessed through specific teleportation capsules, that take you to an abandoned factory where you can fight Vile, The Dragon of the first game. Finding and beating him will result in another boss appearing in his stead later on, where he would normally find and attack you.
    • In Mega Man X6, there's a secret "Nightmare Stage" for every normal level, where you can find secret upgrades and bosses.
  • Prinny: Can I Really Be the Hero? and its sequel has this. Considering that this is that kind of game, they also count as a Brutal Bonus Level. In the sequel, you have to collect a set amount of dolls and it's a lot easier said than done. Thankfully enough, these levels set your lives at infinite, unfortunately, your device and sanity weren't considered.
  • Ratchet & Clank (in Going Commando, Up Your Arsenal, and A Crack in Time) has the Insomniac Museum, a Developer's Room where the game's designers stuck a bunch of stuff that "didn't quite make it into the finished game." The handheld entries (Ratchet & Clank: Size Matters and Secret Agent Clank) have the High Impact Games Treehouse, which serves the same purpose.
  • Roll Away has two kinds of secret level; trippy Bonus levels reached upon collecting five friuts where you have to hit every block, and regular levels IN SPACE reached from secret exits.
  • Skyblazer has a series of secret stages hidden on the overworld map- by going to one of the completed stages and pressing up on the D-pad you'll go to one of the Mode 7 flying bonus stages, which would lead to a secret hut where you could get the game's hidden life upgrade. To get back to the main game and continue with your adventure you have to complete a short 1-screen stage called 'Ship to Nowhere', where you ride a small wooden boat across the lake and have to avoid being washed overboard by huge waves while fighting off the enemies the waves deposit on the deck. Survive all the waves and the stage simply ends, depositing you behind the Lair of Kharyon.
  • Sonic and Knuckles has both secret areas that are only accessible by one of the characters, and a different final stage for 100% Completion.
  • Sonic the Hedgehog CD has the Dummied Out 8th Special Stage. To access it, the player has to enter a code in the title screen to open the secret Sound Test, then enter another code on it.
  • The Super Mario Bros. series has many of its installments featuring secret levels, sometimes in spades:
    • Super Mario Bros.: The Lost Levels has World 9, which the player can access only by playing the first eight worlds without warping. Meanwhile, Worlds A through D are accessed by playing through the main game eight times (in the All Stars version, you go straight to them after World 8 or 9).
    • Super Mario World has many, many secret levels and two entire secret worlds. The secret levels are usually unveiled in the map after finding a golden key in a regular level and placing it in a keyhole to enter a secret exit. In one case (Secret Ghost House in Donut Plains), you have to defeat a hidden Mini-Boss (Big Boo) instead.
    • Super Mario Land 2: 6 Golden Coins has two secret levels in the Pumpkin Zone, and one each in the Tree Zone, Macro Zone, Space Zone and Turtle Zone (this leaves Mario Zone as the only standard world without secret levels).
    • Wario Land: Super Mario Land 3: Starting from this game, almost every game in the Wario Land series has many secret levels, including whole secret worlds (in fact, Mario Land 3 itself has the world Sherbet Land, which is accessed by completing a level from Mt. Teapot via a secret exit).
    • Super Mario World 2: Yoshi's Island has one secret level per world (accessed by 100% completion of the normal levels), generally based around a gimmick, much harder than other levels, or both. The Game Boy Advance remake has another secret level per world once the game has been beaten.
    • Super Mario 64 has various secret levels hidden in the hub area, and one more within one of the regular worlds (namely the one in Hazy Maze Cave, where you find the switch that enables the use of the Metal Cap). The Nintendo DS remake adds even more.
    • Super Mario Sunshine has special obstacle courses within Delfino Plaza that are either hidden in plain sight or require a significant amount of effort to be entered. And save for the sliding course located close to Gelato Beach (which is more of a warm-up level that can also be accessed shortly after the game's prologue ends), these courses are also pretty difficult.
    • New Super Mario Bros. has secret exits that have red flags instead of the standard black flags; reaching them usually unlocks a hidden level (though in other cases they let you skip sizable chunks of the game).
    • In both Super Mario Galaxy and Super Mario Galaxy 2, Hungry Lumas take Mario and Luigi to secret galaxies after they're fed with enough Star Bits.
    • Luigi's Mansion has multiple hidden, secret or otherwise unneeded rooms inside the game, which are essential for 100% completion and getting all of the ghosts, but is often entirely optional and one may even forget to do them while playing because those rooms are never mentioned.

    Puzzle Games 
  • Wonderland Secret Worlds has several secret levels. They're invisible until you locate them on the world map and give out rainbow stars upon completion instead of the usual gold stars. Completing all of them allows you to access Cloud City.
  • Angry Birds has several secret levels accessible through collecting golden eggs, which are hidden in the levels and other areas of the game. Some of them are like regular levels, while others are more esoteric; one is a Rube Goldberg Machine which eventually directs a single Blue bird to blow up the pigs, another has three pyramids of pigs which need to be blown up with only one Red, and yet another has a strange, bouncy floor and ceiling which allows a single bird to bounce around and defeat all the pigs.
  • Gruntz:
    • Each level has areas accessible only with the use of red wormholes (which appear temporarily if you step onto a specific tile) and secret switches (which make parts of the terrain change temporarily).
    • Additionally, it seems that the game was intended to also have actual secret levels. They would be unlocked if a grunt carrying a specific tool (most likely one that is impossible to get on the main level without cheats) steps on a specific tile. However, only one such level made it into the game.

    Racing Games 
  • Walt Disney World Quest: Magical Racing Tour has the Splash Mountain track, unlocked by coming in first twice on the other nine tracks. The game does a good job of hiding it...but not only does the manual tell you how to unlock it, the list of tracks in the back includes Splash Mountain with the notation "Secret Bonus Track". Nobody told the manual writer what "secret" meant, apparently.

    Real-Time Strategy 
  • Age of Empires II has a level based on the Saxon Revolt hidden in the files. It must be imported into the game by following instructions provided by the Read Me.
  • Creeper World 4 has the aptly-named Ever After. The mission can be found by scrolling far, far to the bottom right in the Farsite level-selection menu. It tasks the player with completely de-Creepering a difficult planet and letting all its forests regrow. This marks the start of Danu's new life alongside her AI friends as an eternal defender of the universe, serving as an epilogue for the campaign.
  • StarCraft: Brood Wars features a secret mission which hints at a major plot point in the sequel. It has no lasting impact on the game otherwise. Said sequel also features a hidden mission in the Terran campaign.
  • Warcraft III: The Frozen Throne has a hidden tower defense mini-game. If you defeat all the waves, you will receive a bonus hero in the following level.

    Rhythm Games 
  • Cytus has a number of hidden songs:
    • Many of themare unlocked by interacting with the splash screens of non-hidden songs. Many of these will require a guide or some trial-and-error to discover. They will count towards your chapter and game score and songs cleared totals (in fact, playing every non-hidden song and seeing that the "songs cleared" counter isn't maxed out for that chapter is a giveaway that hidden songs exist), as well as your TP average, but you won't be able to see your records for these songs.
    • The chapter select itself also has hidden songs, triggered by tapping on the Easy and Hard song clear counters.
    • Chapter L got new charts due to players complaining that the original ones were too hard, however the original charts can still be accessed by tapping on the locations of the blinking "L" insignias.
  • In the Friday Night Funkin' mod BETADCIU, there are two examples.
    • First off, in the 8.0 update, a song called "Restore" may randomly pop up in the bonus song list.
    • Secondly, there's some songs that are accessible through effort outside of simple dumb luck. Beating certain songs ("Lament" and "Dusk" in 8.0, "Roots" and "Sorrow" in 8.5 onward) without missing or getting a "bad" rating even once unlocks two different covers of "Deathmatch". The first one has Daddy Dearest's Karma Houdini Warranty finally expire as Senpai gets his revenge with the help of some others, while the other - and the only one that exists in the 8.5 version, with you needing to beat the Senpai version with the same requirements as the chain's start in 8.0 - is a crossover between HoloFunk and Friday Night Funkin': Corruption, which reimagines the final showdown between Daddy Dearest and the corrupted Boyfriend with their HoloFunk equivalents (Aloe in place of Boyfriend, Calli in place of Daddy Dearest, and so on), complete with a corrupted design for Aloe made by Blantados himself.
  • Muse Dash songs normally have three difficulties: Easy, Hard, and Master. However, "MopeMope" has a hidden level 11 chartnote  accessed by tapping on the Master icon until a popup shows up reading "The Ultimate Children's Day Gift".

    Role-Playing Games 
  • Dark Souls has The Painted World of Ariamas, the Great Hollow, and the Ash Lake. For the most part, they're difficult-to-find Breather Levels with lots of really good loot.
  • Lands of Lore 2 has two hidden areas: the Draracle's Museum and the Dark Halls. The first of these contains a bunch of equipment and other goodies.
  • Quest 64 has a secret level in the desert. While in a completely unrelated and skippable area, it does have a ton of powerups which are normally hard to find.
  • Undertale has Hard Mode, a version of the first area with more difficult-to-spare monsters, activated by giving the fallen human the same name as the player character.
  • Wizardry has these in Wizardry 8's three hidden "Retro Dungeons", which take the form of old, grid-based dungeons made as they were in the 1980s using early 2000s graphics. None of them have anything to do with the main plot and some contain monsters not found in the "real" game outside of them, such as golems made from coal, or box-like "kube" monsters which appear to have been made using geography assets from the game's construction kit.

    Stealth-Based Games 
  • "Requiem," the final mission of Hitman: Blood Money. When it starts, it appears to just be a screenshot of 47's funeral over which the end credits are actually playing. Twirling the analog sticks (or pressing "W" on the computer) eventually causes 47 to get up, at which point the credits disappear and the mission begins. (This level is so secret that, on the Xbox versions, an achievement is awarded for completing the game after finishing the previous level. Realizing that there is a mission in "Requiem," and then completing it, is good for a second achievement of equal value.)
  • Sheep, Dog 'n' Wolf has two, both cleverly hidden in the Hub Level. One at the end of a passage in a wall that looks like a completely ordinary wall, and the other accessed by entering one of the doors from the other side.

    Shoot 'Em Up 
  • DoDonPachi Maximum has a hidden level that can be accessed by unlocking Stage 5-E, then setting the difficulty to Easy and tapping on where Stage 5-E would be. It's a Brutal Bonus Level that pits you against stages and bosses from Ketsui and Espgaluda II, culminating in a showdown against Evaccaneer DOOM, the True Final Boss of Ketsui.
  • Gradius, as a series, is flat-out obsessed with hidden levels. Most games in the series have a secret alternate path, usually be doing something during the level to change the boss you fight. This gets lampshades in ReBirth, where you can fight a different boss but end up in the same level 2 stage regardless - the actual Secret Levels (there are three) are much better hidden. Not every game uses hidden stages, but rather Multiple Paths. The self parody series Parodius makes fun of this along with everything else - the secret levels in some of those games are even more insane than the standard ones.
  • Rez has the Lost Area, unlocked by completing all the normal areas. It is quite difficult. Same for Child of Eden's Hope level.
  • The Sharp X68000 port of Fantasy Zone has a secret eighth stage, "Dragon Land," based on Space Harrier.
  • Star Fox has the Black Hole and Out Of This Dimension, both accessible from the two Asteroid Belt stages.
  • Tyrian is absolutely chock-full of secret levels. As a rule, they're accessed by destroying a specific target in a level so that a big glowy sphere appears. When you grab it, you'll move on to the corresponding secret level after finishing the current one. Some of these are tough to get, requiring you to leave certain enemies alone or stay on a certain path. There's even secrets 'within' secret levels, so you can go through a bunch of secret levels in a row before returning to the normal ones.

    Turn-Based Strategy 
  • Advance Wars has a number of such levels which can only be accessed by beating the preceding levels in under so many turns, otherwise you'll just skip over them without even a hint that they're there. Sonja, the one you face in them, is working together in secret with Grit to unravel the mystery of who really started the war, and if you perform well enough in certain levels she'll challenge you to see if you're worthy to be let into the loop. There's also an extra particularly hard level that comes after the final mission, only accessible if you chose Andy for the final mission and had Eagle in charge of the Green Earth troops.
  • Advance Wars: Black Hole Rising and Dual Strike have secret levels accessed only by finding a map in the preceding level, which would be found when you captured a specific property. Sometimes you'd get a hint in the form of the enemy's banter prior (Such as them telling a Mook to make sure it's hidden), while other times there'd be no hint at all and you'd just have to go looking. Finding the map and beating the following mission unlocks Black Hole exclusive units like Piperunners, Neo Tanks, Black Bombs, and Black Boats for you to deploy in later levels

    Wide-Open Sandbox 
  • Saints Row 2 has Revelation, which provides closure to the ending of the first game and is not unlocked through the standard story progression. Instead, you are given a hint to go to the police headquarters, where you can listen to three wiretap conversations and find Dex's phone number, who directs you to the mission start.
  • Terraria has secret world seeds that can be entered on world creation to generate a world with unique properties. These can range from silly cosmetic changes to including entire new mechanics that drastically change how the game is played.

    Other Media 
  • In Sword Art Online, there is a dungeon below the first floor of Aincrad that houses incredibly powerful monsters that don't typically appear until the 90th floor. The leader of the Aincrad Liberation Front, Thinker, gets trapped in this dungeon because of a power-play by Kibaou, who used the dungeon to grind levels in secret.

Alternative Title(s): Secret Stage