I'm in the Google NYC office, which occupies most of a building that's a full city block and 15 stories high (https://en.wikipedia.org/wiki/111_Eighth_Avenue) and that sits on top of a major subway station. We also have floors in a few of the neighboring buildings (Chelsea Market, etc.).
It seems to work really well. The density means that it's not that physically far to go to meet with another team, and that you hear what's going on with completely unrelated divisions.
I'm a little surprised that Silicon Valley overall has stuck with these relatively low-rise, sprawling campuses.