Up on Kulen mountain, about 50 kilometers from Siem Reap, a natural stone bridge crosses one of the small streams that pour out onto the plain below. From this bridge, and for about 100 meters downstream, the ancient Khmers carved linga images into the exposed stone riverbed. The linga is a simple phallic shape, the symbol of the god Shiva and his powers of creation. There are reportedly around 1,000 images in all. They probably served a purification purpose. In addition to the lingas along the riverbed, there are bas-relief carvings in many of the boulders along the stream. The carvings end in a small but pretty waterfall that apparently was once used as a ritual bathing spot by the king.
The landscape around the stream is also rather spectacular in itself. The rocks take many fantastic forms, and there are a few good viewpoints along the walk up to the stone bridge. It's no wonder the place was a hiding spot for the Khmer Rouge in the war years.
Kbal Spean is about 12 kilometers past Banteay Srei. From the parking area, it's about a 45 minute hike up to the carved area. While most of the walk is a gentle slope uphill, there are two rough spots that require some steep climbs.
Note: Although removed from the main Angkor Archaeological Park, you must still posses a valid admission pass to visit Kbal Spean. Kbal Spean closes every day at 3:00 PM.