The OSM Importer lets you import data from the Open Street Map data. This is an open database of most of the planet.
The idea is to use real data to generate representations of existing cities, or to use as a starting point for new cities. A few tools to aid building generation will follow, but the first step is to get the raw footprint shapes constructed or imported.
You can download this tool from our Github Repository
Likely the first thing you'll try to do is extrude the building shapes, but there is a small gotcha on the way the data is being generated. This video will help you sort through that and show you a trick with using the generated data as a random seed.