Caving in Vietnam

Am Tiên Cave is a hidden grotto on the karst hillside above the Hoa Lư valley - reached by a steep climb of 200 stone steps, with a bat colony inside the cave and views from the hilltop over the ancient capital's rice fields and limestone peaks.

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 Vietnam's most spectacular limestone grottos: a 2.1km passage of cathedral-scale chambers, extraordinary stalactite and stalagmite formations, and near-total silence, just 3km from Bản Giốc Waterfall.

Paradise Cave is the longest dry cave in Asia at 31km - a cathedral of white and gold stalactites up to 40 metres high, discovered only in 2005 and opened to visitors in 2010, with a 1km boardwalk through chambers so vast they dwarf everything inside them.

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 - the largest and most spectacular limestone grotto in Ha Long Bay - hides two vast cathedral chambers, surreal stalactite formations, and a panoramic viewpoint over the bay, all inside Bồ Hòn Island in the heart of the UNESCO World Heritage Site.

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.