True, the big academic hospital here is coloured as really old, but the shape of the building is definitely mostly modern additions, parts of which I've seen be

True, the big academic hospital here is coloured as really old, but the shape of the building is definitely mostly modern additions, parts of which I've seen being built while I lived here :) But to properly display that is a real hard problem. First, you need way more data, a complete history of the changing shapes of buildings as they were being reconstructed/renewed/etc, over the ages. Second, how to visualize all of that? Layer all of it on top of eachother, with old at the bottom and newer shapes covering it, maybe? or ... stacked in 3D, like a geo/archeological excavation! Right now it seems a bit of a compromise, mashing up two datasets that don't always properly "fit" together. But on the whole, on average, and for many aesthetic purposes, it does a very good job.