The Ghost Town is a location in Grand Theft Auto: San Andreas, located within the Hidden Interiors Universe, situated very far up in the sky above the height limit for airplanes, somewhere over the ocean near San Fierro.
The Ghost Town is simply a small poorly-detailed portion of Portland from GTA III, containing a few buildings and roads surrounding Marco's Bistro. Some of the surrounding buildings are only partially rendered, and have low-poly textures; some of which aren't even solid. During the mission Saint Mark's Bistro, Carl Johnson flies to Liberty City to assassinate a high-ranking member of the Forelli family. Since the only area needed to render for this mission was the restaurant, game designers only made the restaurant, and a few buildings and roads nearby, to give the illusion the player is really in Liberty City.
Accessing the Ghost Town
During the Saint Mark's Bistro mission, the player is confined to the restaurant and it's backlot, meaning he cannot exit the area and go beyond the restaurants boundaries to explore Liberty City. However, the player can enter the Super Jump cheat (KANGAROO) and jump over a wall in the back lot. From there, the player will be able to jump to the road in front of the restaurant and explore Portland. The Jetpack cheat is ineffective, as this particular interior is situated higher than the game's aircraft height limit.
Unfortunately, there are some sections of the Ghost Town that are not solid, and the player can fall through them. It is advisable to bring an automatic weapon with lots of ammo, as the player can decide if an area is solid or not by shooting at it. If there is sparks, then the area is solid, and if there are none, the player will clip through. If the player happens to fall through the ground, they will fall for a few minutes, and land in the ocean near San Fierro, however, the whole world will be invisible because the player will still be in the Hidden Interiors Universe. The only way to get out is cheats or mods.