The capital of the Khmer empire for a brief period from 928 to 944 AD, Koh Ker lies within a day-trip distance from Siem Reap. This ancient city, which is believed to have had a thriving community of over 10,000 inhabitants in its era, now remains isolated from the other attractions of the area. The main attraction of this site is the Prasat Thom, a pyramid-like structure, on to which you can climb and revel in the splendid views across the surrounding forest. Many tourists visit Prasat Krahom, the second largest structure of this ancient city, for its striking stone carvings and elegant window columns.