The GeoJSON export is a pretty exciting.  Haven't looked at the
GeoJSON spec yet but it seems weird to have the bldg coords in an array of arrays with those having a single element that is an array of arrays.  Expected the coordinates themselves to be in a JSON object like {"x":0.05; "y":0.03}. But maybe that's the spec.

Also, are the coordinates in unit space?  i.e. -1 to +1, x & y, in the "world" plane?  Probably an RTFM for the spec question.

Anyway, looking forward to experimenting with bringing the JSON into a VTT and seeing about drawing the city dynamically instead of importing a static image.