The old Silicon Graphics building is now the Computer History Museum.
I wouldn't say "The old SGI building". I'd say one of them, a building that SGI acquired that was closer to the main freeway (on the same street as a major Silicon Valley Microsoft campus) with intentions of using it for marketing.
The main SGI buildings were a mile up the road, away from the freeway, closer to (or most recently right on top of) the Mountain View sanitary land fill.