Concierge.com's insider take:
The most exquisite carvings cover the Bayon. Like Angkor Wat, this masterpiece was constructed in the 12th century; it's topped by 54 stone towers, each bearing four smiling, enigmatic faces and clad with intricately carved bas-relief panels. The Bayon stands at the exact center of the walled city of Angkor Thom, the final capital of the Khmer Empire. To avoid the crowds, visit Bayon in the early morning or afternoon. For a total Lost City experience, proceed for one mile on the unpaved paths heading due east or west from the Bayon. They both lead through forest to massive, rarely visited gates crowned with the same happy faces. Well worth the brief detour.