Angkor Wat is the largest religious building in the world, located in Cambodia. It was built in the 12th century as a Hindu temple but later became a Buddhist temple. For over 400 years, Buddhist monks lived at Angkor Wat and prevented the jungle from overgrowing the temples. Though its original purpose is unknown, historians and archaeologists continue to study Angkor Wat to learn more about the Khmer Empire that constructed it over 1,000 years ago.