The powerful Khone Pha Peng waterfalls can be viewed over several kilometres to the south of the island of Don Khone, in the most southerly part of the Mekong in Laos. These impassable rapids, the highest of which is an impressive 20m, remain the main obstacle to river navigation between China and the delta, in the south of Vietnam. The falls are at their best during the dry season as they are completely obscured by the water during the monsoon.