Collection of 31 Prefab, 21 basic to make more variations and 10 combined buildings to give you start point to make your buildings.
All buildings use 3 materials: Top, Side and Glass.
Glass material can be tweaked with tiling parameters to get more building variations. Side material can be also tweaked with parameters to set number of tiling sectors.
To change windows simply make one 4K texture and use 256*256 squares and place window in each square. Replace Window texture and you will get new building windows very easy.
Check out the details from the Unity Asset Store: https://assetstore.unity.com/packages/3d/environments/skyscrapers-1-137158