A three-hour car ride away from Siem Reap, Koh Ker is home to the ruins of an ancient city. At Koh Ker, you can visit the pyramid temple complex of Prasat Thom and Prang. This old city is home to many temples, buildings, and other monuments and was a thriving town home to over 20,000 people.Tickets cost 10 USD for foreign tourists, while guides are an additional 5 USD.