Cities Skylines is a very special game. I sunk way too many hours into this and still enjoy it on occasion.
There’s a nifty plugin that allows to overlay a png image with transparency so one could hobble together a map with imported heights data from e.g. NASA and overlay it with streets, rivers and train tracks from e.g. Google Maps.
This results in recreation of real cities within the engine bringing the hardware to it’s limits.
There are also hundreds of downloadable assets in the workshop.