Cobweb Jungle

In horror and adventures movies, any subterranean area must be filled with quantities of web curtains, overflowing with colonies of mad spiders on speed who quickly fill every nook with webs, like an arachnid Mardi Gras. Catacombs, caves, basements, tombs, underground ruins (but not, oddly enough, Underground Levels), etc. show this, even though these are rather hostile environments for web-building spiders. Although collective or very large webs are known, they occur outside. Not to mention that such large webs in such quantities are useless: Webs are delicate in order not to be too visible. The type of spiders usually shown are unlikely to build webs of that type anyway.

May be used in any kind of story to indicate that no one has been in a place for a long time. If the character is retrieving something, the object will be covered with cobwebs to show that no one has touched it in a long time.

Note the subtrope that people never get too covered with them: They seem to be easy as pie to clean off in the absence of water, except for the stylish bit that gets stuck to the hair or hat.

Can overlap with You Have to Burn the Web, Extremely Dusty Home.

Comic Books

 * Elf Quest's Forbidden Grove is covered in sticky webbing. Turns out it's not made by spiders, though.

Film

 * Used cleverly in the 1931 Dracula, where Bela Lugosi seems to pass right through a large spiderweb without breaking it. No F/X involved, just a well-timed cut between views.
 * The scene is parodied in Dracula: Dead and Loving It, with Renfield awkwardly stumbling through the web and getting caught in it.
 * Nearly averted in Eight Legged Freaks: The only time when we really see any cobwebs is when a character gets the Idiot Ball and has to be blinded.
 * Gremlins 2. One gremlin has metamorphosed into a spider/gremlin cross, and has filled a corridor with exactly this kind of webbing. Naturally, the two hottest girls in the movie walk into the stuff.
 * Don't worry; Gizmo saves 'em after growing a pair and dressing up like Rambo.
 * Indiana Jones
 * Once at the beginning of Raiders of the Lost Ark, complete with absurdly out of place tarantulas. ("Never too-covered" is avoided: as Indy runs from the giant boulder, he goes through a door-wide web)
 * In several caves of Indiana Jones and the Last Crusade. Their extraordinarily thick presence at The Breath of God is required for the plot to work, but still nonsensical otherwise.
 * National Treasure Under  spider webs can be seen all around.
 * The Descent
 * In The Neverending Story, Bastian goes into the school storage area (not the basement), which is rife with spider webs, with no spider in sight. He doesn't seem particularly yucked out when he has to brush gobs of it off in order to open the window.
 * Joked about in the 1963 Roger Corman comic Poe film The Raven-- when going into a very web-shrouded part of Erasmus Craven (Vincent Price)'s house, Dr. Bedlo (Peter Lorre) quips, "Tough place to keep clean." (Lorre improvised much of his dialogue for the film).
 * Despite taking place both in a jungle-esque enviroment, and in caverns the Wizards of Waverly Place movie only sees spiderwebs once for a throw-away gag to highlight Alex' hypocrisy.
 * Young Frankenstein. Massive cobwebs appear in the passage leading to Dr. Frankenstein's laboratory and the laboratory itself.
 * Played for laughs, like everything else, in UHF.
 * Played with in the first Mortal Kombat movie. One hero insists that they person they're following went down a cobweb-criss-crossed corridor, despite none of the webs being broken...

Literature

 * Take to extremes in Simon R. Green's The Gods Of Haven, where Hawk And Fisher must hunt monsters in tunnels overgrown by "Crawling Jenny": an amorphous carnivorous life form made up of cobwebs, fungus, and moss.
 * Shelob's lair from JRR Tolkien's Lord of the Rings. Though ironically the book mentions that she had woven them too thick and didn't get sustenance because of it. Oh, and the web was hard enough to almost twist Sam's sword out of his hand after hitting it.
 * The strength of the web may or may not be justified by her gigantic size, depending on whom you ask.
 * More ridiculous is the fact that webs firmly hold creatures that are, pound-for-pound, several times stronger than humans; yet in the movie, Frodo (a halfling/hobbit} squirmed his way out of Shelob's web with slight effort.
 * Might have something to do with the fact that Frodo had a super-sharp elven sword with him that he used to cut the webs quite obviously - no squirming took place in the scene.
 * Ungoliant's lair was also filled with webs, but somewhat different. Her webs were apparently made from "woven darkness", and were designed to capture (and keep out) light, which she fed on (and feared and hated). Similar to Shelob, it was said that she'd eventually woven her webs too thick for any sustenence to actually reach her (although she doesn't really seem to need to eat).
 * In Gormenghast the flooded attic, making Flay and Swelter's fight an Interesting Situation Duel.

Live Action TV
"Willow: Uh, ah! Cobweb! Okay that part was realistic.
 * One episode of Hannah Montana has Hannah/Miley singing in a backstage area for the Hollywood Tone Deaf Lily. This backstage area happens to be home to a giant spiderweb, and therefore a bunch of tarantulas - and, as Miley apparently has a raging case of arachnophobia, hilarity, of course, ensues. This particular web is slightly different from the others, in that it's one huge web instead of a thin sheet of fuzzy stuff - although the web is visibly made up of tied-together ropes, and 90% of the spiders are recognizably props.
 * In the very first episode of Merlin, Mary Collins (Disguised as Lady Helen) sings an enchantment to the courtroom, making everyone fall asleep. Cobwebs start forming over everyone who falls victim.
 * In Primeval series 3 episode 6, Connor walks right into one of the cobwebs in the underground bunker under the safehouse.
 * Buffy the Vampire Slayer. The Scooby Gang enter a frat house that's been turned into a Haunted House (for real, unknown to them).

Oz: Frat boys aren't too obsessive with their cleaning. Might not be decoration per se."

Video Games

 * In the Abandoned Mineshafts that can be found in Minecraft, cobwebs are omnipresent, and rather tough to break without a sword.If they suddenly thicken, you just found a lair of venomous cave spiders.
 * Caves in Terraria often feature large amounts of cobwebs, though they're fragile and only slow down the player for few seconds.
 * Interestingly enough Terraria has no spiders.
 * Heavily present, but arguably justified in the roguelike Ancient Domains of Mystery. Even a handful of the (exclusively giant-sized) spiders present in the game fill up a cavern with obstructively sticky webs quicker than you can type "You hear a slurping sound." However, since the narrow, narrow corridors in the Caverns of Chaos are absolutely swarming with adventurers, robbers, demons, spirits and all manner of predators of all sizes, you can hardly blame the things.
 * In Diablo II, parts of the Spider Forest in Act III.
 * The Wesrin's Cross level in Dungeon Siege. Not only is it a Cobweb Jungle, but a lot of the spiders may only have two hit points, but attack in large enough swarms to be a threat.
 * The "Arachni's Haunt" dungeon of Guild Wars: Eye of the North involves burning webs (and egg sacs) in order to draw out the titular boss monster.
 * Some dungeons, especially the Great Deku Treem in The Legend of Zelda Ocarina of Time and the Spider Houses in Majora's Mask, which are places taken over by spiders Skulltulas.
 * Tomb Raider has these in 2, 4 and Legend (the original, perhaps oddly, does not, despite its Indiana Jones inspiration), although 2 is the only one with actual spiders, including a certain sequence entirely based around this.
 * Spiders are back in Underworld, played straight in the level  but somewhat averted later in the game; Giant Spiders are present in ruins, but webs are relatively rare and most are near the surface.
 * The Varrock Sewers dungeon in Runescape requires the player to slash through a spiderweb blocking the passageway to get into the deepest parts of it. one of the rooms beyond is populated by (surprise!) giant deadly red spiders.
 * Fully justified in Deadly Creatures, where you play a spider.
 * Zombies Ate My Neighbors features many levels strewn with webs and annoying spiders of varying degrees. The spiders are all enemies, but the webs vary as far as interaction: Some are decorative, some narrow your path, some block your path, and some make your feet stick to the floor, as seen here.

Web Comics

 * In Drowtales, the "forbidden level" (AKA Mel's Room), as seen here and here. Justified in that Mel is the resident crazy spider lady.

Western Animation

 * Not only is the Great Owl's lair in The Secret of NIMH covered in cobwebs, but the Owl himself is covered in them too. How long does this guy sleep, anyway?

Real Life

 * Truth in Television as arachnologists found out at Lake Tawakoni.
 * In Pakistan, spiders trying to escape floodwaters were driven into trees, creating this.

Religion

 * Invoked by Allah himself in one of the very few miracles stated to have happened around Muhammad is, when he was escaping the city of Mecca and the Qraysh who were out to kill him, that he and his friend Abu Bakr hid in a tiny cave. Their pursuers followed their track to the entrance of the cave, but in the meantime a spider had woven her web all over the entrance and a dove had set her nest there. They decided that clearly no-one had gotten in there, and resumed their search elsewhere.