I visited Circle Gallery when I visited San Fransisco this summer. The Building is a little known, little published work of Frank Lloyd Wright from 1940. It is located on a small side street off of Union Square. A small sign at the lower back of the interior of the gallery warns that the building is made of plain, unreinforced concrete. The Gallery has changed use many times over the years, from a jewellery shop, to art gallery and on my most recent visit, selling native American Indian artifacts. It was clearly a precedent for the Guggenheim Museum of New York, with the use of the spiral viewing ramp overlooking the central space.
The facade is beautiful in its simplicity, where subtle patterns in the brickwork make a great impact.
I've seen a few of Frank Lloyd Wrights residential buildings in Chicago as well as the Guggenheim and they always amaze and impress me.