I found a lot of interesting tutorials about how to import terrains from the real world into Blender.
What about the buildings of the cities?
A friend told to me you can use another approach to import your city map into Blender. You can make a screenshot of the place, you wanna use and using Adobe Illustrator or Inkscape turn it into vector graphic (.svg) and import into Blender.
I did something better than that. I used the tool Maperitive, selected an area on the OSM and then I converted the file to .dae format, this is the result that I get :
As you can see, there is no separation between the vertices, so when I extrude the points this is what happens :
It's not good at all. I know that I can go on the Open Street Map web site, select an area, export it to OSM file and then import it in Blender, but the problem is that a lot of areas (including the area where I live which is my biggest interest) aren't mapped; because when I try to import it I see only a small geometry.
So, what's the fastest and nicest way to do this?