There are mods for the game that let you easily import height maps. I want to sa...

pjc50 · on Oct 31, 2016

http://terrain.party/ (currently down): lets you turn freely available geodata into a PNG that the game accepts.

It doesn't handle the roads, that was almost certainly done by hand.

maxerickson · on Oct 31, 2016

In the reddit thread they say they took a screenshot of Google Maps and used that to lay out the roads.

There is a mod to import OSM data though, I guess it isn't heavily maintained: