Caving in Vietnam

Am Tiên Cave - nicknamed 'Tuyệt Tình Cốc' after its wuxia-film-like scenery - is a dragon-mouth-shaped grotto above a jade-green lake in the Hoa Lư valley, reached by around 200-250 stone steps, with a dark history as an execution ground under Đinh Tiên Hoàng and a later connection to Queen Dương Vân Nga's Buddhist retreat.

Dark Cave is Phong Nha's most adventurous experience - a zip line over the Son River, kayaking into a pitch-black cave, swimming through underground passages, and a mineral mud bath inside the cave chamber, all packaged into one of Vietnam's best adventure activities.

Ha Long Bay - Vietnam's most iconic landscape and a UNESCO World Heritage Site - is 1,553 square kilometres of emerald water, nearly 2,000 limestone karst islands, sea caves, and floating villages in the Gulf of Tonkin.

Hang En is the third largest natural cave in the world - 3km from Sơn Đoòng, accessible by 2-day 1-night trek through jungle and Bru-Vân Kiều village, with a night camping on a white sandbar inside the cave under a 145m ceiling. The accessible alternative to Sơn Đoòng.

Nguom Ngao Cave - 'Tiger Cave' in the Tày language - is one of northern Vietnam's finest cave experiences: a system with three entrances, surveyed at over 2km and explorable in full along a roughly 3.3km guided route, with dense stalactite and stalagmite formations and near-total silence, just 3km from Bản Giốc Waterfall.

Paradise Cave (Động Thiên Đường) is one of Asia's longest dry caves at 31.4km - the 'underground palace' discovered in 2005 by a local man following cool air from a rock crevice, opened to visitors in 2010. A 1km wooden boardwalk leads through chambers up to 100m high, with stalactite formations resembling Buddhist figures and Champa towers.

Phong Nha Cave is the oldest cave in the Phong Nha-Kẻ Bàng UNESCO World Heritage Site - a 7.7km limestone grotto with an underground river, navigated by wooden boat through chambers of stalactites, with the Son River flowing turquoise below.

Son Doong is the largest cave in the world - big enough to contain a 40-story skyscraper, with its own weather system, jungle, and river inside. Access is by expedition only, with a strict annual quota making it one of the most exclusive natural experiences on earth. All tours run exclusively through Oxalis Adventure.

Sung Sot Cave (Surprise Cave) - the largest limestone grotto in Ha Long Bay at nearly 12,200 sq metres - hides two vast cathedral chambers, stalactite formations tied to the legend of Thánh Gióng, and a panoramic viewpoint, all on Bồ Hòn Island. Named by a French scientist in 1901.

Thien Cung Cave - the Heavenly Palace Cave of Ha Long Bay - spans nearly 10,000 square meters across multiple chambers filled with elaborate stalactite formations, ancient legends of the Dragon King, and a narrow entrance that opens into one of Vietnam's most striking underground landscapes.

Trang An is Vietnam's only UNESCO dual World Heritage Site (natural and cultural, 2014) - a labyrinth of karst peaks, jade rivers, and ancient caves navigated by wooden rowboat. Known as 'Ha Long Bay on land' and a filming location for Kong: Skull Island (2017).

Trung Trang Cave is the largest accessible cave on Cát Bà Island - a 300-metre limestone grotto inside the national park with exceptional stalactite and stalagmite formations, a bat colony, and a history stretching from local legend to wartime military use.