Arguably the crown jewel of the Mekong River tour, the Angkor Wat stands just outside the city of Siem Reap. A UNESCO World Heritage Site, the Angkor Wat also happens to be the world's largest temple complex. The religious site includes a three-mile moat, concentric walls, and the main temple. Today, the temple stands as a much-lauded representation of traditional Khmer architecture and is iconic of Cambodia. Do keep in mind that, the temple is still an active one, so one should cover the shoulders and legs when entering.