Glitch City

Wrong Warp Glitch Cities
are a type of Glitch City in Pokémon Red, Blue and Pokémon Yellow. These Glitch Cities appear when the game uses an invalid entrance or exit point for a map (i.e. one that doesn't exist).

This can be achieved through the Safari Zone exit glitch or by modifying the address D365 (D364 in Yellow), either through cheating, through changing the quantity of item 36 in an expanded items pack (for English versions), or through arbitrary code execution.

An expanded items pack can be achieved through a method such as the item underflow glitch (which is probably the 'cleanest' method of item expansion).

The Safari Zone exit glitch only allows access to a few warp hex:04 Glitch Cities, but modifying the address D365/D364 (the last location to load the player for certain exits) allows the player to access more.

Specific Glitch Cities
These are specific Glitch Cities accessible through the Safari Zone exit glitch.

Glitch City (Go to: Sea Route 20) Glitch City is fairly navigable compared to other 'regions'. Do not try to cut down any trees or enter any caves - trees regenerate, and caves do not work. Entering the nearest one causes you to get trapped.

Glitch Mountain (Go to: Cycling Road) Glitch Mountain is also fairly navigable. Like in Cycling Road, your character is constantly moving downhill. Because of this, you cannot Surf on any of the blocks of water.

Glitch League (Go to: Indigo Plateau or Route 23) Glitch League is not as easily navigable as Glitch City or Glitch Mountain. You can only move around a very small area, but you can see pieces of statues, water, and all kinds of other stuff.

Traits
Glitch Cities accessed through the Safari Zone exit glitch happen when the game places the player at an invalid 'exit point hex:04'. Fuchsia City has a valid exit point hex:04, which is on the Safari Zone building's door.

This is why when the player lands their final Safari Zone step in Fuchsia City, or without changing the value of D365/4, walking out the Safari Zone gate will have the game take the player to the Safari Zone door without loading a Glitch City.

Furthermore, certain locations such as Cerulean City have a valid exit point hex:04, so landing the final Safari Zone step there will make the player step out of a building, such as Cerulean City's Bike Shop.

Wrong warp Glitch Cities are not unique locations, but rather a temporarily corrupted version of an existing map.

This can be proven by viewing the memory address D35E (D35D) in Yellow, and looking up the value here. Additionally, when a player checks the Town Map while in a Glitch City, the map says that they are in the source map.

Also, attributes of the source map are preserved. The Cycling Road Glitch City forces the player to move downward, in the same manner that the Cycling Road itself does. The tileset of the map is the same as the source map. The sizes of the map are preserved as well.

Wild Pokemon are also preserved; if the source map had wild Pokémon data, then those Pokemon will appear when Surfing in Glitch City. If the Glitch City had a 'left-facing strait tile', it is possible to perform the left-facing shore tile glitch with it. This is possible with the Sea Route 19 Glitch City. Missingno. and other Pokémon can be made to appear in a Glitch City via the old man trick.

A number of interesting changes are made to the map when it is corrupted. Some of these are relatively obvious, while others are more subtle.
 * All terrain in the map is corrupted beyond recognition.
 * Warps and objects are ignored and do not appear in Glitch Cities. This is why doors, signs, and cave entrances do nothing when they appear in Glitch Cities, and why people never appear in Glitch Cities.
 * Objects are anything on the overworld that takes up space and can be interacted with using the A button. People and cuttable trees are objects. There are also invisible objects that are placed over signposts -- signs, like doors, don't do anything on their own.