Jurgen, try going into the David Rumsay collection listed in links. The US Geological Survey at http://topomaps.usgs.gov/ might be of aid as well. I don't know what type of libraries and research centers you have near where you live, but looking for old geological and survey maps might be of help. One other thing, should you be lucky enough to get ahold of scans of the type of maps you are looking for, try to create tiles of the features you wish to use if you have Photoshop. One fellow was able to reproduce 3.5 Forgotten Realms style maps of his home campaign world using that method. It was very sharp and professional looking.