Angkor Wat 101: Everything You Need to Know About Visiting What Was Once the World’s Biggest CivilizationWhat's the best way to Angkor? How do you plan for visiting Angkor? The ruins of the Angkor temples, built from the 9th to 15th centuries, are a must-see. At its height in the 13th century, the city of Angkor is estimated to have had a million residents, and the kingdom covered almost all of Southeast Asia, making it that era’s largest civilization. UNESCO named the Angkor Archaeological Park, situated just outside of Siem Reap, Cambodia, a World Heritage Site for good reason. The key to enjoying it, though, is escaping the crowds.