675 California St.

Date built: 1964

via John King, San Francisco Chronicle:

675 California St. is a small modernist jewel box on the edge of Chinatown facing St. Mary's Square. No skyline presence, no big architect, just nice slice of International Style design.

Architectural historian Vincent Scully once likened the essence of International Style modernism to "an uncomplicated intellectual order." You see this at St. Mary's Square, where the neighboring structures include this clean jewel of steel and glass. It looks less like a building than an immaculately tailored suit, and it remains a fresh counterpart to thick masonry and the ever-present cable cars. An especially deft touch is the circular staircase; placed in the most visible corner, it makes the interior life of the building part of the overall design.