Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Royal Keep Free.
Royal Keep 1.0
The location includes 1,067 objects, and has 112,715 polygons, 79,226 vertexes.
All textures in TIF file format. 512×512.
You can enter the palace and every house and tower, or climb the ramparts. The palace has 3 floors.