Like LA itself, Los Santos is a patchwork of neighbourhoods with a downtown area, a gang-infested southern district, and the prosperous areas in the hills. But the game world extends out into the fictitious state of San Andreas, Rockstar's interpretation of southern California. There are farmlands, deserts, villages, mountains; there is even a functioning ecosystem teeming with wildlife. Trevor lives in a stinking shack out in Blaine County, a deserted coastal region, modelled on California's Salton City. The first time we meet him, he's on the john having a noisy bowel movement; Rockstar never shies away from these sorts of details.
Importantly, the whole map is open from the start. Players can take a chopper and fly out over the hills, parachuting down onto the peak of Mount Chiliad. They can jet-ski, mountain bike, play golf, exercise. They don't have to, they just can.