Charles Fort called it the Super-Sargasso Sea; the dimension into which lost things go. Amelia Earhart's over at the bar. The Lost Colony of Roanoke is next door. USS Cyclops? In the harbor. Elvis Presley? Who do you think is on stage? The Dead Sea Scrolls? Have a pamphlet. And everybody has all the socks they could possibly need. Just not matched ones.
This is a place all adventurers In Harm's Way wish they would end up, and everyone else wishes was just a fantasy; the multiverse's biggest attic/basement/toolshed. Everything is here. Starships, Indigo Children, misfit toys. It's a Portal Crossroad World where it's easy to enter but significantly harder to leave. It's a Derelict Graveyard that people actually live in. It's a Landfill Beyond the Stars where the crap never stops gathering. It's everything you could possibly want mixed with all the stuff you hoped you'd never see again.
Often accessible via The Bermuda Triangle.
- Oblivion Island from Oblivion Island: Haruka and the Magic Mirror is where neglected objects from our world end up being used by the inhabitants who can't make them themselves.
- In The Familiar of Zero, lost objects and people from Earth often end up in the alternate world of Halkeginia. Earth technology is highly prized due to the world's low technology level.
- Daring Do and the Journey to the Center of the Earth has the Temple of the Lost. The protagonists go there to find Pinkie Pie's missing body, and they have to sort through loose change, missing socks, and other assorted junk first.
- Sakaar in Thor: Ragnarok; in the Marvel Cinematic Universe, any Blind Jump will add you to the endless stream of junk falling from the myriad portals hovering above this Landfill Beyond the Stars.
- Halloweentown II: Kalabar's Revenge reveals that anything misplaced in either Halloweentown or the mortal world ends up at the house of Gort the ogre.
- In Finders Keepers by Emily Rodda, the protagonist visits the world where things go when you put them down a moment ago and can't find them again.
- Harry Potter has a variant in the form of an endless room filled with objects that people at Hogwarts have hidden over the years — though it all gets destroyed in the final book with a good dose of wizard napalm.
- Mary Poppins and the House Next Door has Mary Poppins take the Banks children to visit her uncle, the Man in the Moon, who hoards physical items lost on Earth.
- Un Lun Dun is set in a city where lost objects from London go. Other cities have their own Super Sargasso Seas.
- The Border Sea from The Keys to the Kingdom is full of lost object from the secondary realms.
- The Land of Lost Objects in Eerie, Indiana is located at the center of the Earth and is run by the US government that steals objects to promote consumerism.
- An episode of Charmed has the Halliwell sisters using a spell to find lost things backfiring to the point that everything they ever lost came back, thus turning their house into this trope. It starts off fairly normal, returning lost jewelry and countless missing socks, but quickly runs to the ridiculous when their grandmother's dog who went missing years before turns up out of nowhere and Phoebe's blonde hair, dyed in the kitchen sink, suddenly reverts back to brunette.
Phoebe: So, technically, I lost it here and now I've found it again. *beat* I hope this doesn't affect my virginity.
- In Ben Lear's Lillian: A Folk Opera, the narrator believes that everything lost winds up eventually in the Great Pacific garbage patch. He journeys there to find a vague something that he thinks is missing from his romantic relationship.
- Dungeons & Dragons (BECMI) module IM3 "The Best of Intentions". One of the planes the Immortal PCs may have to travel to is Unsoncy. The center of the plane is a rotating disk of debris that comes out of a singularity in the middle. Items lost on other planes of the universe end up here. The Immortal who controls the plane always looks here first when he loses a pair of socks in his washing machine.
- Dark Void. Aliens, lost ships, Nikola Tesla. It's all in the Void. The hero even enters via The Bermuda Triangle.
- In Touhou, the barrier surrounding Gensokyo works such that it attracts things or concepts which have "become fantasy" in the outside world. While it's mainly a justification for the existence of youkai, it also attracts other things like extinct or endangered species, and yes, a bunch of lost items from the outside.
- In text adventures there is usually a location which the player cannot reach, containing all the objects not currently in play. In the ZX Spectrum game Shadows of Mordor, it is possible (by design or mischance) for the player to travel to this location — the description reads 'Frodo is nowhere'. It isn't possible to leave again.
- This is how the titular Submachine behaves, with its architecture being comprised of a mishmash of ancient ruins from multiple civilizations.
- The Massive underground Ocean in the Neath from Sunless Sea might well be one of these, being seemingly unconcerned with things such as time, space and causality. A lot of things to be found there seem to be plopped haphazardly from other places in space and time. Aside from entire cities, such as London, there are also Eldritch Abominations, the Skeletons of massive unknown...things, and A pair of Sphinxes implied to be from Egypt and somehow related to the famous one in Giza.
- The many manifestations of the Drains in Pact are places where forgotten things go, even gods forgotten by their former worshipers, and where Others such as bogeyman are formed.
- On the search for Cassie's missing dad, Marion and Cassie from Bounty Hamster find themselves in the world of the lost. Not only are lost objects there, but people too: there's a room of lost dads and even the antagonists that the duo 'lost.'
- A sock-oriented variant appears in one episode of Jacob Two-Two. Jacob finds an Alternate Dimension where all the missing socks go. Here, they use socks as currency, and there's even a black market for them.
- A literal Land of Lost Objects appears in The Real Ghostbusters.
- In Peter Pan & the Pirates both the Lost Boys and the Pirates enter a group of caverns in Neverland that is indeed the Land of Lost Objects, where they even met Captain Hook's lost childhood.
- In The Ren & Stimpy Show episode "Black Hole", Commander Hoek and Cadet Stimpy go through a black hole and end up in a strange dimension, where they find a pile of all of Earth's missing left socks.
- The Bikini Bottom Triangle in the eponymous episode of Spongebob Squarepants contains many items taken by the mermaids via singing to activate a giant vacuum, which opens a rift in the sky while doing so. When they sing their song backwards, the items are returned to their owner.