After importing a map into the viewer you can simply enjoy viewing it in 3D - that was its initial purpose.
Or you can export a city as an .OBJ file and then import it in some real 3D software. For example, you can modify and render it in Blender to get nicer images, or you can use it in Unity as a part of environment in a game.
And that's it, the viewer itself doesn't provide tons of opportunities :)