Phnom Sampeau would be an interesting place even if it weren't for the rather grisly recent history. The hill rises sharply from the flat surrounding countryside about 14 kilometers south of Battambang, affording a great view of Battambang and the rest of the countryside.
The saddle-backed hill has temple complexes on both of its peaks. The temple on the slightly lower peak is built over a complex of caves, which are the focus of the grisly recent history. The temple's prayer hall was used by the Khmer Rouge to house prisoners - the people that were considered educated, rich or just rubbed them the wrong way. The prisoners were interrogated, then thrown down into one of the caves. Those that didn't die from the fall had no way out and so eventually died from starvation. Many of the bones of those that died are collected into two large cages in an adjoining grotto, which also has a reclining Buddha image.
The temple on the higher point of the hill is perched right on the edge of the cliff. The complex consists of several towering pagodas, all of which seem to be rather new. There are no bone collections here, but there are two gun emplacements that were used to help beat back the Khmer Rouge.
Admission to the hill area is US$2 for foreigners. You can either climb the 650 steps up to the top, or you can rent a motorcycle with driver for US$5. If you decide to go on foot, you're technically required to have a guide.