As I am in the middle of redesigning a kitchen with my significant other and just spent many hours looking at hurking slabs of rock in near three-digit weather (I picked a garnet granite in the remnant yard), my contribution to this version of the Accretionary Wedge (#10) are two of the buildings in downtown LA that had some of my favorite geology in architecture.
The first is 601 Wilshire, or the Figueroa at Wilshire: http://skyscraperpage.com/cities/?buildingID=1357
Construction was finished in 1990, and the architect was Albert C. Martin. As monolithic downtown office buildings go, this is one of my favorites. I spent many hours both inside and in the outer courtyard of this building, faced with pink granite apparently from Brazil (also used on the inside). My favorite building feature: the pink marble sconces in the hallways, sliced thin to be translucent and give a warm pink glow to the interior. I've craved marble sconces like that since, and just raved about them again to a friend, while discussing use of stone in the home.
The other is the Los Angeles Public Library: http://www.lapl.org/central/art_architecture.html
I also spent many hours in this building, constructed in 1926 by architects Bertram Goodhue and Carlton Winslow in that quintessential southern California meets Egypt style, like many other buildings in SoCal constructed during that era. It apparently had an arson fire in 1986 and was restored to be called the Richard Riordan Library. Unfortunately, the websites don't have a discussion of the floor tile, a beautiful Devonian shale/slate apparently quarried in the British Isles. I don't quite know if this is correct, as I emailed the docents and received that info in reply. It is a beautifully calming dark green clearly showing the sedimentary structures contained within the stone. I've also craved a floor of this, to bring calm to home and a reminder of the ebb and flow of the tides and the seas.