To use any sort of structure, every being on Earth needs it to have an entrance, and so do most things in fictionland — whether they be rabbit holes, anthills, dragon caves, skyscrapers, a space station, or just about any other structure, all have entrances to facilitate their use.
Therefore running into a structure clearly intended to be used, but without any sort of entrance, is a bit of a lurch, and immediately gets across that whatever this structure is, it was not usable for the average corporeal muggle: Maybe whatever uses the structure has Intangibility powers; maybe they use Teleportation to teleport directly inside, maybe the builder Failed a Spot Check when going over the design documents, or maybe the structure once saw use, but was sealed up so thoroughly that it doesn't even register that it used to have an actual entrance - in which case, you've probably found the one of the many types of can and should think twice about proceeding without knowing which one.
A common subversion is for the structure to have no apparent entrance until The Chosen One, or someone with the right McGuffin approaches, whereupon the structure reveals itself to be a case of Only the Worthy May Pass as an entrance becomes apparent, probably leading to a Secret Room; this subversion is common because it turns the act of entering from an impossibility if you don't possess alternate means of entering, to 'merely' a puzzle for the characters to unlock. In this case, someone who does possess an alternate means of entering, for instance teleportation, is likely able to perform a Dungeon Bypass. Though, unluckily for the heroes, these characters tend to be villains, giving them a head start on whatever the structure contains.
Attempting to create a Sealed Room in the Middle of Nowhere, a Super-Trope, counts as this only if there is no entrance left after the sealing - merely locking the only way out isn't enough - neither is having a surface with visible locks but no visible entrance, as the existence of a lock means that it, by necessity, must open something. Outside these subversions, Anti-Structure or Barrier-Busting Blow is generally going to be the only way to actually access the building for those lacking the otherwise intended means of ingress, though More Dakka can prove a viable solution by way of Bullethole Door, and this is one case where blowing open a hole in the wall is generally seen as justified, averting There Was a Door entirely.
Not to be confused with Gateless Ghetto (urban areas with no entrance in video games).
- A Certain Magical Index: Academy City's Windowless Building can only be entered by a specially trained teleporter, as it's armored against attacks. Although, a few breaches do happen.
- Doctor Fate: Doctor Fate's headquarters, the Tower of Fate, has no doors, and can only be accessed by the use of magical teleportation.
- In Lucifer (2000 series), when Lux, the title character's L.A. headquarters, burns down, he dispenses with the "nightclub" front and rebuilds it as a private fortress without doors. After this, others can get in only by invitation or unspecified supernatural power. The one exception is a teenage couple who, believing it to be God's home on Earth, get in by climbing the exterior until they find a glassless window. However, they soon find they can't get back out, and die of thirst within three days.
- Dungeon Keeper Ami: Multiple:
- Ami starts out in a buried dungeon and has to dig her way out.
- Ami makes secret labs that only she can enter, through teleportation.
- Ami's prison cells sometimes don't have doors, as she can free her prisoners by teleporting them out.
- The Adamantine box is a sealed room Made of Indestructium.
- In the Hyperion Cantos, the Portal Network of the Hegemony allows for the creation of such structures. In the second book, the leader of one religion builds such a shelter for himself deep inside a mountain to live in comfort until the end of the world his church expects. Of course, he gets a massive Oh, Crap! moment when the end of the world doesn't come... but the collapse of the Portal Network does.
- The house of the Portico family in Neverwhere is designed to be impenetrable, and consists of numerous disconnected rooms that can't be reached by normal means, designed to be accessed by the family's special Open and Shut ability. Unfortunately for them, Messrs. Croupe and Vandemar are able to use their Offscreen Teleportation ability to bypass this.
- The Witling: Axhiri buildings usually have no entrances since their main mode of transportation is Swap Teleportation with themselves and the air of their location.
- In the Buffy the Vampire Slayer episode "Fear Itself", a fraternity house is under a spell where the doors and windows disappear. To enter the house, Giles takes a chainsaw to one of the walls.
- The Goodies: In "The End", the Goodies's office accidentally gets completely covered in concrete, ironically as part of an architectural design of Graeme. This leaves them living inside a giant block of concrete, awaiting rescue from the outside, which isn't coming because budget cuts force the government to scale services back by 100%.
- Drake & Josh: In "Tree House", Drake, Josh, and Megan are tasked with rebuilding a neighbour kid's tree house after they accidentally blew it up with a rocket. The duo manage to complete the tree house, except Drake forgot to cut out an entrance in one of the walls and leaving the saw outside trapping them inside, with a pissed off Megan torturing them on the outside because they made her miss her friend's birthday party.
- In the video cassette adventure intended to be an introduction for the players into the world of Dragon Strike the heroes come across a dwarf imprisoned in Terraptus's fortress. Agreeing to release the fellow, the Warrior asks where the door to the cell is, prompting this delicious response:
Dwarf: There is no door you...
[devolves into angrish before calming down]
Dwarf: You only make a door if you plan on releasing someone. [Terraptus] never planned on letting me go!
- Fallout 4: Despite most of the Commonwealth looking for signs of one for decades, an entrance to The Institute was never found, and the only remnants of the original Commonwealth Institute of Technology are bombed-out ruins. That's because The Institute has no physical entrances. Getting in requires teleporting in and out several hundred feet below ground.
- The Legend of Zelda
- The Legend of Zelda: A Link to the Past: The Swamp of Evil, which houses the Misery Mire dungeon, is completely blocked off from the rest of the Dark World by impassable barriers, with a sign warning Link that there is no way in and no way out. Within the limits of the Dark World, it is indeed completely unreachable. However, Link is able to get in by traveling to the Desert of Mystery -the swamp's Light World counterpart- and finding a portal between the worlds there that crosses into the swamp.
- The Legend of Zelda: Twilight Princess: The Gerudo Desert is accessible only via Oocca cannon, and once inside, can only be exited by warping away. Although Auru does mention that there was a road there that's been cut off
- The Main Gate in Mega Man Legends is totally impregnable at first, with no indications at all of how to get it. Once it is unlocked, the entire outside lifts away, revealing the door underneath.
- In Outer Wilds, the core to the Ash Twin, which contains the Advanced Warp Core powering the 22-minute time loop, is physically sealed off from the outside with a protective shell of mined Timber Hearth ore, with no physical entrances in sight. According to the notes left behind by the Nomai, this is to make the core as supernova-proof as possible, and the only way in is via one of the warp towers on Ash Twin's surface.
- The Protoss of Starcraft use teleportation incredibly casually. While most of their structures have entrances, their warzone-deployed structures specifically lacks them: It keeps the Khalai caste workers safe from internal sabotage and infiltration, meaning that the only two ways to disable the building are to destroy it or cut the power. Not that there is any sort of infiltration play in the actual gameplay for any of the three races.
- Kouka And Bibi: The fox and raccoon hide from their pursuers in a room—then to make absolutely sure no one follows, the fox pulls the entire doorway off, leaving a solid wall behind. After that, they look around and realize the room now has zero doors or windows. Fortunately, the fox also has a jackhammer, so they're able to make their own exit.
- The Tangean Overworlders of Buzz Lightyear of Star Command take their name from the fact that they have Intangibility as a species trait, and thus they simply walk through the wall of any building they mean to enter. They see this as inherent proof that they're Blue Blood, and anyone who doesn't know how to enter a building is just not worth associating with, whether they be Tangean Grounders or just outright aliens.
- The Fairly Oddparents: In "Truth Or Cosmoquences", Timmy, Cosmo, and Wanda travel to Fairy High for the Cosmo's high school reunion, with Timmy suffering a massive Potty Emergency not long after from drinking too much lemonade (The reunion's theme being "A Tribute To Running Water" doesn't help matters either). When Timmy tries to find a bathroom, he finds out all the doors are just painted on, as Wanda explains that since they can just poof in and out of places there's not really a need for real doors. However, fairies are seen using doors in other episodes of the show that came before and after this one.
- One episode of The New Adventures of Winnie the Pooh has Rabbit get so fed up with his friends that he builds a huge wooden fort to keep them out. He realizes too late that he forgot to build a door for him to exit through; the rest of the episode deals with Pooh and the others trying to create an opening.
- On The Simpsons, Homer tries to build a doghouse, but is constantly failing. At one point he appears to be successful, until Lisa points out that he forgot to put in a doorway.
- Marvel Comics has Uatu the Watcher observe humanity from his home on the moon. When the Fantastic Four came to ask where Reed Richards had gone, they found Uatu's home to be a featureless dome with no sign of an entry point. Hothead Johnny Storm mentions that he could burn a hole in it, but Sue admonishes him that the way to enter Uatu's home is to simply walk in: the dome is almost immaterial, designed to keep out dust and dirt. Sapient creatures can pass through it as easily as air.
- Arcia Chronicles: The Lightbringers' towers in Tarra appear as stone monoliths with no obvious means of ingress. However, when an elf (or some other magic user) carrying the talisman of the corresponding Lightbringer approaches their tower, a door will magically appear on its surface, which can then be unlocked with said talisman to enter.
- Monday Begins on Saturday: the NIIChaVo building has no visible doors or gates unless a resident mage wants to show you how to enter or drive in.
- In the Michael Crichton novel Sphere the titular object is a perfectly sphere with small indentations on the surface. It becomes an important plot point when a character is seen entering the Sphere with the indentations being revealed to indicate the location of a door.
- In Tolkien's Legendarium:
- Dwarves in general build their caverns with stone doors, indistinguishable from the surrounding natural rocks, and so skillfully made that no cracks or other signs are visible when the door is closed.
- In The Hobbit, the secret back door to the mines of the Lonely Mountain only becomes visible in the light of the setting sun, on one specific day of the year.
- In The Lord of the Rings, the door to the mines of Moria is decorated with ithildin, which only reflects moonlight and starlight, leaving the door invisible during the day (and on cloudy nights).
- The Wheel of Time: The Tower of Ghenjei is a seamless 200-foot-high column from the Age of Legends, now used only as a landmark. The main characters eventually work out that drawing a particular symbol on its side with a bronze dagger causes the symbol to "open" into a portal to the world of the Aelfinn and Eelfinn.
- Critical Role: Wildemount: The Archmage Yussa Errenis lives in Tidepeak, a 450-foot-tall Mage Tower with no doors or windows. He or his assistant can cause a door to appear when it's convenient for them, but he prefers that "select friends" visit via Teleportation Circle.
Fishmonger: It [appears] when they come in and out, but then it's gone. It's really creepy.
- Star Wars Rebels: The Jedi Temple on Lothal has no apparent entrance and looks more like a strange rock outcropping than a building until approached and opened by a Jedi apprentice and their master. If they lose focus while inside the entrance(s) will be hidden and it will take both of them to open it again, explaining the several dead knights and masters in the foyer.