I made them in XFrog, which is really for trees, but with a little experimenting you can get something that looks like buildings and boats, seen from a distance. Some parts are done up in PS. I'm also looking for more detailed medieval (and stone age) buildings for close-up views, can't make them myself.
The most time-consuming part of this render was to get about 60 buildings exactly into the right spot (I had a map from the client), at the right angle and height. One by one, testing, change a little, testing, change a little, testing, next one.............................. bloody awful.
---Dune