345 California Center is the third tallest tower in San Francisco. The building is a 37 floor office building with an 11 story Mandarin Oriental Hotel on top.
The six sided tower actually sits mid-block on four sides and it is surrounded by four much older historic midrises. The tower breaks at the hotel into two square rotated prisms. These two towers at the top are connected by glass skybridges. The hotel towers are capped by offset spires which form what many say looks like a pair of tweezers.
The tower was the largest tower in the city built in the 1980's and the last 600'+ tower built until 2008! By roof height (630ft) it would be the 5th tallest in the city.
I like the form of this building (particularly the hotel portion at the top), but the way that the tower sits amongst its neighbors at the base is just odd. The street entry is set WAY back from California Street in a deep dark plaza and the angular facades meet the sidestreets in an odd manner.
One of these days I've got to go and stay at the Mandarin Oriental. I really want to see the city from the skybridges.