SFist today has a map of POPOS, Privately Owned Public Open Spaces downtown. Some look really cool.

• 1. Redwood Park: An urban park at the foot of San Francisco’s most striking skyscraper with redwoods, sculptures and a fountain.
• 6. 343 Sansome Street: Two open spaces, one a sun terrace on the 15th floor (with an obelisk), the other a lunchtime mall.
• 21. Crocker Galleria: Two rooftop sun terraces, one on an historic bank building, the other “accessed from an obscure staircase in the northwest corner of the Galleria”.
• 30. 50 Beale Street: A “rather large” urban park full of trees and bushes, and including a railroad car housing a Bechtel Corp. museum.

If I still worked in the FiDi, I'd get on that.