I'm not sure those are renders of the same content. Just similar ideas.

The second one is a Poser render from 2002. Whatever it's made from is probably not available any more.

Agree that it looks like primitives with a transparent green shader. There are all kinds of city and castle models available, but this doesn't look like any of them. No windows, doors, insides, etc. They're just smooth and solid. I'm guessing the artist just assembled primitives like cylinders, rings, spheres, etc. into a city.