Cambodia’s most dramatic cascade, Bou Sraa waterfall is a fabulous two-tiered cascade some 35km from Sen Monorom, towards the Vietnamese border. The setting alone makes the falls worth visiting, the river dropping over 30m into a jungle gorge. Getting there is something of an expedition, however, making it easy to see why the locals get around by elephant. Not nearly as dramatic as Bou Sraa, but a whole lot easier to get to (though the road is unsurfaced and can be tricky after rain), are the three-tier Romanea falls.
Just 4km northwest of Sen Monorom is the 10m-high Monorom waterfall (also known as the Sihanouk falls). Along the way you’ll pass the ruins of the (rarely used) royal residence, after which you should follow the left fork to the falls. You can swim in the pool at the base of the falls, even in the dry season.