River Quay Son, some 300m wide and 50m high, forms the most stunning waterfalls in Vietnam, Ban Gioc Falls. The water accumulates in tiers of pools in a mountainous landscape pitted with rice paddies, and you can swim at the foot of the waterfalls. The border between China and Vietnam is at the centre of Song Quay Son and Vietnamese boats can only sail on half of the river. In the middle, a narrow strip is accessible to boats of both nationalities.