Angkor Wat is a large Khmer temple built by King Suryavarman II in the 12th century. It was dedicated to the Hindu God Vishnu and was meant to represent Mount Meru, home of the Hindu Gods. Originally a Hindu temple, it eventually became a Buddhist temple in the 14th or 15th century after the fall of the Khmer Empire. The structure itself is nearly a mile long. It is the largest religious structure in the world.
Today, Angkor Wat is the top tourist attraction in Cambodia. It even appears on the national flag. It was named a UNESCO World Heritage Site in 1992.