GTA 2 (1999) included only one fictional city, named Anywhere City. This city was divided into three districts. Last 2D GTA before jumping into 3D.
What it was
Three districts contained within one city. Overhead camera perspective. Gang reputation meta-game. Relatively limited scope by the series' post-2001 standards, but a clear progression from GTA 1's three cities into one concentrated locale.
More influential for its gang mechanics than its map design.