Concierge.com's insider take:
The apotheosis of Khmer civilization, 12th-century Angkor Wat remains the national symbol of Cambodia. It's well worth spending at least half a day here. Make sure to see the Churning of the Ocean of Milk along the East Gallery, an epic bas-relief describing a tug-of-war between gods and demons to turn the ocean into an elixir of immortality. Like Ta Prohm and Bayon, Angkor Wat is on the heavily traveled tourist circuit. Ask your driver to take you to the eastern gates instead of the busier western gates.