Here's the old and new juxtaposed in San Francisco: Twitter's 295k SF HQ in a Shorenstein-restored building from 1937 they moved into less than two years ago. It's revitalizing the formerly seedy mid-Market neighborhood, and inspired other moves by Square, Spotify, and Yammer. Oh, and so did the exemption the city offered from the 1.5% payroll tax.
The other thing attracted to the block: 35-story NEMA (for "New Market"), 754 high-end apartments. One bedrooms: $3,500, going fast. This here's San Francisco, housing shortage capital of America.