GTA 3 invented the modern GTA template. Three boroughs, gradual unlocking, full 3D city. Twenty-five years later it's still recognisable in what GTA 6 is doing.
Three boroughs, gated unlock
Portland, Staunton Island, Shoreside Vale - unlocked across the story. The progression-as-map-reveal pattern that GTA games still use was invented here.
Each borough had distinct visual coding - Portland gritty, Staunton Island commercial, Shoreside Vale wealthy. The pattern of region-as-character was set.
What GTA 3 set up for everything after
Free-roam city with story progression. Distinct district personalities. Vehicle missions. Pedestrian density (modest by 2026 standards but transformative in 2001).
Vice City and San Andreas would expand on this. GTA 6 still operates inside the GTA 3 template, scaled up enormously.