Please provide a link similar to http://www.openstreetmap.org/#map=18/45.69288/9.66530 showing the area you're missing.
I would say the position of the screenshots in Bergamo is this:
http://www.openstreetmap.org/#map=16/45.6910/9.6598
You can take as reference the triangular building in OSM that appears on the left of abassign's screenshot.
The city center of Bergamo (LIME) is dense, but I could not reproduce it, as you can see there is a limitation in the number of houses or something, but I can not find in the parameters.
From a quick look it appears you are not seeing buildings because they're not mapped in OSM.