This is a paid asset, but now you can download Small City 3 Free.
Detail this asset from Unity Store: Original Link
Small City 3 v1.0
“If possible, please buy the package to support the developer”
Huge collection of 73 models for your games. There are 15 houses, 45 city props, 14 vegetation models.
All houses share only 4 atlased textures for fast rendering.
With all these additional models you can expand this city and make really huge leves.
To get same look like in our video you need to bake lightmaps and use some post processing effects.