Gittes' Office
In case anyone is curious, the building(s) used for Jake Gittes' office are here:
http://maps.google.com/maps?sourceid=navclient&rlz=1T4SUNA_enUS256US256&um=1&ie=UTF-8&q=5608+S.+Soto+Street,+Los+Angeles+CA&fb=1&split=1&gl=us&cid=0,0,10258249327579101943&ei=0IO7SYG5FYm4sAP6jNw4&sa=X&oi=local_result&resnum=1&ct=image
It appears they used both buildings. The exterior is 5608 S. Soto and at least one interior (with the curved corner window) is inside the building directly south of it.
The art department did a nice job of distracting the viewer from the more modern buildings nearby by putting that oil rig in the parking lot!
What lovely art deco bon-bons they are!