Hidden Interiors Universe

The Hidden Interiors Universe refers to an area in Grand Theft Auto: San Andreas which houses all the hidden and shown interiors in the State of San Andreas. The universe is located very high in the sky, past the height limit of aircraft, and all interiors are organized into different sections. The normal game world is invisible if the player drops down to it.

Places
The Hidden Interiors Universe is located very high in the sky. Whenever the player walks into a yellow bouncing ENEX marker to enter a home or building, the player is transported to the corresponding interior within the Interiors Universe. Whenever the player is inside an interior, he is inside the Hidden Interiors Universe.

If the player finds a way to exit the interior without going through the door, and he drops down to the ground, the whole world will be invisible.

Even though the interiors universe is a place itself, it contains many markers that allow the player to enter another place or hidden interior in the state of San Andreas.

In San Andreas, there are 150 hidden interiors located in 18 different universes, or as they are called, heavens. These include:

Heaven A

 * Ganton Gym- start of hidden interior
 * Diner
 * Well Stacked Pizza
 * Victim
 * El Quebrados Police Station
 * Madd Dogg's Crib
 * Crack Den
 * Vank Hoff Hotel
 * Burning Desire House
 * Many Burglary houses can also be seen.

Heaven B

 * 2 Brothels
 * Blastin' Fools Records
 * Las Venturas Police Department
 * Las Venturas Planning Department
 * Johnson House
 * B Dup's Apartment
 * Helena Wankstein's Farm
 * Jizzy's Pleasure Domes
 * Tattoo Parlor (Las Venturas)
 * Barbers
 * ProLaps
 * Sex Shop XXX
 * Inside Track
 * The Big Spread Ranch
 * Wheel Arch Angels
 * Burglary Houses

Heaven C

 * Loco Low Co.
 * Reece's Hair & Facial Studio
 * Caligula's office
 * Katie Zhan's House
 * Ryder's House
 * B Dup's Crack Palace
 * Big Smoke's Crack Palace
 * Safehouse
 * The Pig Pen
 * Several Burglary Houses

Heaven D

 * Los Santos Forum
 * Below the Belt Gym
 * Ammu-Nation
 * Burglary House

Heaven E

 * Liberty City
 * Sub Urban
 * Warehouse
 * Ammunation
 * Ten Green Bottles
 * Doherty Garage
 * Caligula's Palace
 * Burglary House
 * Denise Robinson's House
 * Shamal
 * Sweet Johnson's House
 * Sindacco Abattoir
 * Safe House
 * Wu Zi Mu's Apartment
 * The Welcome Pump
 * Hyman Memorial Stadium- it appears in Vice City, but does not appear in San Andreas.

Heaven F

 * Burger Shot
 * San Fierro Police Headquarters
 * The Four Dragons Casino, and the Janitor room appears as well.
 * RC Battle Ground
 * 24-7
 * Motel Room

Heaven G

 * ZIP
 * Atrium
 * Lil' Probe'Inn
 * 24-7
 * Warehouse

Heaven H

 * Alhambra
 * Hemlock Tattoo
 * Jim's Sticky Ring
 * Sherman Dam Generator Hall

Heaven I

 * 24-7
 * Tattoo, Los Santos

Heaven J

 * Binco
 * Jefferson Motel
 * Corvin Stadium
 * Burglary Houses

Heaven K

 * Area 69
 * Normal World, San Andreas


 * Gasso Gas Station

Heaven L

 * 24-7
 * Palomino Creek Ammunation
 * Burglary Houses
 * Michelle Cannes's House
 * Dirt Track Stadium

Heaven M

 * Barber
 * U Get Inn Motel
 * Casino Floor
 * Safe House

Heaven N

 * Zero's RC Shop
 * Los Santos Police Department
 * Cobra Marital Arts
 * Millie Perkins' Home
 * Brothel
 * Secret Valley
 * Ammunation
 * 24-7

Heaven O

 * Safe House
 * Colonel Fuhrberger's House
 * Burglary House

Heaven P

 * Cluckin' Bell
 * Andromada
 * Prickle Pine Safehouse
 * Unused Safehouse
 * Burglary houses

Heaven Q

 * Misty's
 * The Four Dragons Management Room
 * Safe House

Heaven R

 * Wardrobe
 * Los Santos International Airport
 * Francis International Airport
 * Kickstart Stadium
 * Didier Sachs

Vehicles
Vehicles are only visible if they are specifically made to exist in that universe. Cars are normally invisible in the interior world, however there are a few certain times they are visible. These include:
 * Sentinel - Saint Mark's Bistro
 * Forklift - Breaking the Bank at Caligula's
 * PCJ-600 - during the mission Stowaway
 * A Car in a Mod Shop
 * A Car in a Stadium event
 * S.W.A.T. in End of The Line
 * If the player manages to store cars, and go to the Doherty Garage whilst in the interior world then the player can drive the car, but cannot see very well.

Also note that in the interior world the player cannot spawn a car using cheats. A "cheat activated" sign will appear, but no car will be spawned. It is possible to spawn cars in the interior world using trainers.

Entrances
There are various methods for exiting an interior and being able to explore the interiors universe freely. However, some of these methods require the use of a Jetpack, and this ability may not be available in some interiors, since they may be higher than the height limit for Jetpacks. Therefore, a trainer or mod for an infinite height limit may be required.
 * The easiest method for entering the interiors universe is by going to the Ganton Gym in Los Santos. A small section of the interior's ceiling right above the front door is not solid. The player can stand under this section, equip himself with a Jetpack, and then fly upwards, and he will go through the ceiling and enter the interiors universe. Note that it is essential to kill the four people inside the interior, otherwise the jetpack will not work properly.
 * In the Prickle Pine safehouse in Las Venturas, the ceiling area above the front door and in the main hallway is unsolid. The player must enter the "Jump Higher" cheat, since this particular interior is higher than the game's height limit, rendering the Jetpack useless. The player must jump towards the door, and he will go through the ceiling.
 * Inside one of the maintenance rooms in Caligula's Palace, there is a small open air vent which is used in the mission Breaking The Bank At Caligula's, in which CJ drops grenades through the vent to knock out the security guards in the room below. This vent remains open after this mission. With some difficulty, the player can jump through this vent and appear inside the interiors universe, although this may take many attempts.
 * Inside the Jefferson Motel, there is a skylight inside one of the lobbies that gets shattered by the SWAT team in the mission Reuniting the Families. After this mission, the skylight remains open. The player can jump through the skylight and entering the interiors universe by entering the "Jump Higher" cheat, and then jumping from a potted plant or couch on the other side of the room. If done correctly, CJ will jump through the skylight and land on some solid area on top of the interior.
 * Similarly, if the player looks straight upwards through the same skylight, he may see a save icon floating in mid-air. This save icon actually belongs to the Hashbury Safehouse.
 * Inside the Atrium in Downtown Los Santos, if the player enters it, equips a pistol, and then walks backwards through the door whilst aiming the pistol forwards, he will walk right through the front door and back outside. Although, technically, he will still be in the interiors universe.

Trivia

 * The interior universe contains many places and interiors, some are used, others are not. One such example is a warehouse, which was never seen in GTA San Andreas. The unused places could have been made for the Beta, though.
 * The color of the sky will often change when the player enters yellow markers, for example, entering the large warehouse interior will make the sky appear blue.
 * Many unused, deleted versions of common interiors are found in the interior world, such as a few unused 24/7's, an Ammunation with two floors and a safehouse.
 * Most interiors are in this sky, but some are located inside their actual buildings or under the ground, some of these include The Welcome Pump, Abandoned AC Tower, Sherman Dam Generator Hall, Lil' Probe Inn, Atrium, CJ's garage in Doherty, the Area 69 interior and both cutscene rooms from the Four Dragons Casino.
 * A small section of snowy Liberty City appears in the Saint Mark's Bistro mission in GTA San Andreas. Outside of this mission, the location can be accessed via a non-solid section of the Ganton gym.
 * Dropping down from any interior in the sky will cause the player to fall for about one minute and will eventually hit San Andreas and be wasted. Alternatively, the player may also fall into water.
 * A handful of Interiors, such as the Atrium, are special because their respective buildings have windows on them, which you can see through. However, to achieve this, game designers had to place the interior of the building inside the actual building and render the immediate area surrounding the building to a certain radius away from it. For example, in the Atrium, if the player is in the interior and he looks through one of the large windows, he may see the street in front of the interior, along with a few buildings, trees and objects in their respective places. However, the player may notice that he cannot see beyond a certain point. This is because a small section of Los Santos surrounding the Atrium is still rendered around the Atrium, so it can be visible if the player looks outside, for a touch of realism. However, this method was not used for designing all interiors in San Andreas, because they are located in the sky, and as a result, most of the interiors (such as The Johnson House, Burger Shot, etc.) have windows that you cannot see through.
 * GTA San Andreas is not the only GTA game with a hidden interiors universe, some examples are GTA Vice City and Vice City Stories.
 * In GTA San Andreas when you enter an interior (in the normal world), the game will load the interior from the Hidden Interiors Universe.
 * It is currently impossible to reach these interiors in the Mobile version of the game, because cheats cannot be used.
 * Strangely, after being wasted in the Interior Universe, you will still spawn in a hospital at any point in San Andreas.
 * Try entering the Driving School found in San Fierro. You will see pedestrians inside of it. Then, walk back out through the front door and climb onto the roof. If you wait long enough, you will suddenly see the pedestrians that were inside of the Driving School plummeting to the ground. This is because, when on the outside, all interiors become textures, allowing for the pedestrians to fall through the ground.