Koh Ker is one of the most impressive day trips from Siem Reap. One ticket gives access to a whole ancient Khmer capital with a climbable pyramid, quiet jungle temples, brick towers wrapped in tree roots, stone elephant guardians and red forest roads.The biggest surprise was how empty many temples felt. There were some people near the pyramid, but at other stops we were almost alone among ancient ruins. Very different from the busiest Angkor temples.The Koh Ker ticket was $15 for one day and separate from the Angkor Pass. Buy it at the entrance booth before driving deeper into the park. Bring cash, water and enough time. A car with a driver is more comfortable than a motorbike, especially if returning late.