Microsoft’s main campus is actually east of Seattle and Bellevue.
Seattle = Bunch of skyscrapers to the west of lake Washington (also includes the Space Needle).
Bellevue = Smaller bunch of skyscrapers east of lake Washington (this also includes a few Microsoft buildings).
Just north of Bellevue runs the WA-520. If you follow it west across the lake you get to Seattle. If you follow it east instead it curves towards the north into Redmond, and that’s where you’ll find the main campus.
West of the 520 you’ll find this group of buildings next to a soccer field:
That’s the Microsoft Commons (basically a small mall/food court) in the middle surrounded by Studio A, B, C and D, and building 92 (the visitor center).
East of the 520 you’ll find many other Microsoft buildings, many of which don’t exist anymore in real life because the campus is being extensively remodeled so right now it’s just a construction site. Also missing from the sim is light rail construction and a new pedestrian bridge across the 520, also under construction. I suppose eventually the photogrammetry data will get updated with all the new construction. 
I work in Studio A, the building on the bottom right of the four similarly shaped buildings surrounding the commons. Well, normally I do; currently I work from home along with most of the rest of Microsoft. 