Located in Ganton, Los Santos, the gym becomes accessible following the mission Drive-Thru. Carl Johnson can learn boxing moves at the gym, as well as use the other facilities to increase or decrease certain statistics, specifically stamina, muscle and fat.
- There is a small unsolid section of ceiling right above the entrance inside the interior. One common use for the gym is the hole in the roof which allows access to Hidden Interiors Universe, which requires the player kill everyone inside, using the jetpack cheat code to acquire a jetpack, and walking towards the door with the jetpack, lifting the player off into the Universe. Using this the player can enter several non-used interiors, you can even enter Liberty City, which is a left-over interior from the mission Saint Mark's Bistro.
- Park a car with its front end touching the front door of the gym, and then walk into the marker to enter the gym. Then, when inside, exit the gym, and one will spawn inside a small room behind the front door of the gym, which is normally inaccessible to the player. The walls aren't solid, and if one walk through them, they will fall into the Blue Hell, and then spawn outside of the gym on the sidewalk.
- In a beta screenshot, the boxer that the player can challenge had a much different appearance, wearing long pants and a bandana. He also just stood upright instead of punching the bag.
- In the same beta screenshot, one can see that the yellow posters around the room aren't there and there is a pedestrian walking around. This suggests there were going to be ordinary people in there as well as the boxers and the spectator.
- Its interior is actually located in Red County, close to Catalina's Hideout. If the player drops down from the Hidden Interiors Universe, a shovel can be found.
- The player can be damaged and eventually wasted if the heavy bag was pushed ends up hitting them repeatedly. The same can be done to the boxer.