And here you can see the part, which is hidden and does not need lots of polygons and modeling.
This stone has about 100,000 triangles, so at the end of the work, I must used the Multires modifier to reduce the poly count to about 30%, which was enough so there is no visible differences on the final image.
I used this Modeling Technique for all main objects in the scene.
Here is animated gif of the modeling process of the upper object which covers main building.
