The Rise and Fall of the Khmer Empire: Who Built Angkor Wat?

Angkor Wat is the largest religious monument on Earth, and it's on Cambodia's national flag. The empire that built it once ruled much of mainland Southeast Asia, including a big part of today's Thailand. So how did the Khmer Empire rise so high, and why did it fall? From the year 802 on Phnom Kulen, to the water system that fed Angkor, the Cham invasion of 1177, Jayavarman VII and the Bayon, a Chinese envoy's notes on daily life, the four big reasons for the decline, the "lost city" myth, and the hidden city that lasers found in 2012.