Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Town Constructor Pack Free.
Town Constructor Pack
This modular town constructor packs includes:
1) 100+ Modular parts for creating random modular buildings & roads.
2) 40+ Props for streets.
3) 30 Drag&Drop premade buildings.
4) 1 Demo scene with buildings, props, roads & basic lighting included.
5) Everything has its prefab with materials included. material contains optimized diffuse, specular & normal maps.