The Royal Palace and the two magnificent pagodas in the Palace Grounds, the Silver Pagoda and the Temple of the Emerald Buddha, are among the few public buildings in Phnom Penh really worth seeing. They were built in the 19th century with French technology and Cambodian designs, and have survived the traumas of the 20th century amazingly intact. See them early before it gets too hot. They are in any case closed 11:00-14:00, when all sensible Cambodians take a nap. Entrance fee is US$6.25 for both. No extra fee for camera. No photography is allowed inside the Silver Pagoda and some of the Palace buildings. You're expected to dress decently, but you can rent sarongs and oversized T-shirts for a token 1000 riel (plus US$1 deposit) at the entrance.