The cave capital of the world — where Son Doong, the planet's largest known cave, contains its own cloud forest and river inside its passages, and hundreds of undiscovered chambers remain in a UNESCO karst
Phong Nha is a small town in Quảng Bình Province, central Vietnam, and the gateway to Phong Nha-Kẻ Bàng National Park (UNESCO World Heritage). The park's 944km of ancient limestone mountains hide more than 300 caves, including Son Doong — first fully explored in 2009 — which at 9km long and 200m wide is the world's largest cave by volume, with its own weather system, underground river, and jungle of 30m trees. Paradise Cave (31km of explored passage), Phong Nha Cave, and the Tu Lan cave system are accessible without specialist permits.
Phong Nha-Kẻ Bàng's limestone karst is among Asia's oldest, formed some 400 million years ago in the Devonian period and sculpted by underground rivers over millions of years. Phong Nha cave served as a Cham Hindu sanctuary before Vietnamese settlement — carved Sanskrit inscriptions date to the 9th–11th centuries. During the American War (1955–1975), the cave network sheltered Vietnamese field hospitals and provided cover for logistics along the Hồ Chí Minh Trail. Local farmer Hồ Khanh discovered Son Doong in 1991; a British Cave Research Association expedition fully mapped it in 2009, reveal…