Koh Ker is a complex of several temples, but the star of the show is the huge stepped pyramid of Prasat Thom, the largest in the area. Built by King Jayavarman IV, Koh Ker was briefly the capital of the Khmer Empire from 928 to 944 AD. One of the appealing things here is the complex was left to the jungle for nearly a millennia and is mostly unrestored. The result is an overgrown picturesque state of ruin. It also sees much fewer visitors than the main temples. Koh Ker is a 2-hour drive (130km) from Siem Reap and is best combined with a day trip with Beng Mealea, and possibly Preah Vihear. If you want to take your time you can make a two day trip with an overnight stay in Sra Em. Wear good shoes for this, not flip flops. If you wander into the grassy areas, watch out for snakes! There are two small simple restaurants outside the entrance, and obviously, the price is at a premium due to the remote location. Many tour operators in Siem Reap offer trips to Koh Ker, or you can hire a private taxi. Entry: $10 (Angkor Archaeological Pass is not valid).