The 3d Tokyo website linked here the other day (https://news.ycombinator.com/item?id=21188767) also shows you buildings when you zoom in, I'm guessing the guy didn't gather this data himself for such a hobby project, but got it from some governmental survey source.

Capable governments should already have that sort of data, e.g. the Swiss one: https://www.swisstopo.admin.ch/en/maps-data-online/maps-geod...