Phong Nha Cave
Phong Nha Cave is a cave in Phong Nha-Kẻ Bàng National Park, a UNESCO World Heritage Site in Quảng Bình Province, Vietnam. It is 7,729 metres long and contains 14 grottoes, as well as a 13,969 metre underground river. While scientists have surveyed 44.5 kilometres of passages, tourists are only allowed to explore the first 1500 metres.
