Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download City Buildings Free.
City Buildings v1.0
This pack contains a set of 25 building prefabs in different shapes, sizes and styles for populating a cityscape. Their low poly count makes them especially useful for blocking out background areas in your environments.
The pack also contains some bonus prefabs which you can use to add even more variation to the buildings, including 2 rooftop huts and a satellite dish!