This fabled limestone outcrop 12km southwest of Battambang along NH57 (towards Pailin) is known for its gorgeous views and mesmerising display of bats, which pour out of a massive cave in its cliff face. Access to the summit is via a cement road or – if you're in need of a workout – a steep staircase. The road is too steep for remorks. Moto drivers hang out near the base of the hill and can whisk you up and back for US$4.
About halfway up to the summit, a road leads under a gate and 250m up to the Killing Caves of Phnom Sampeau, now a place of pilgrimage. A staircase, flanked by greenery, leads into a cavern, where a golden reclining Buddha lies peacefully next to a glass-walled memorial filled with bones and skulls – the remains of some of the people bludgeoned to death by Khmer Rouge cadres and then thrown through the skylight above. Next to the base of the stairway is the old memorial, a rusty cage made of chicken wire and cyclone fencing and partly filled with human bones.
On the summit, several viewpoints can be discovered amid a complex of temples. As you descend from the summit's golden stupa, dating from 1964, turn left under the gate decorated with a bas-relief of Eiy Sei (an elderly Buddha). A deep canyon, its vertical sides cloaked in greenery, descends 144 steps through a natural arch to a ‘lost world’ of stalactites, creeping vines and bats; two Angkorian warriors stand guard.
Near the westernmost of the two antennas at the summit, two government artillery pieces, one with markings in Russian, the other in German, are still deployed. Near the base of the western antenna, jockey for position with other tourists on the sunset lookout pavilion. Looking west you'll spy Phnom Krapeu (Crocodile Mountain), a one-time Khmer Rouge stronghold.
If you visit on your own, a local guide may try to escort you around the sites and give you some history. Phors is a good guide who works for donations, with US$3 being appropriate for an hour-long tour.
Back down at the hill base, people gather at dusk (around 5.30pm) to witness the spectacle of a thick column of bats pouring from a cave high up on the north side of the cliff face. The display lasts a good 30 minutes as millions of bats head out in a looping line to their feeding grounds near Tonlé Sap. Note that there are lots of monkeys at this site, and you should not be flashy with your food, as angry monkeys have been known to become aggressive.