Built during the ninth century at what was the center of the royal city at the time, Phnom Bakheng (also known as the temple of Shiva) is one of the oldest temples in Angkor. The five-tiered pyramidal structure, built on top of a hill, and was originally surrounded by 108 towers, an auspicious number in many Eastern religions.
While the temple ruins of Phnom Bakheng are impressive, the reason most visitors come is to watch the sunset from the top or to attempt to snap the money shot of Angkor Wat rising up from the jungle in the distance (the site sits less than a mile from Phnom Bakheng). To avoid the crowds, consider coming at sunrise instead.
Practical Info
Getting to the hilltop temple requires a somewhat steep 15-minute walk, but for a fee, you can also ride an elephant to the top. If you come for sunset, bring a flashlight for the climb back down.