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. The only way to see it properly is by overnight cruise.

Hang En is the third largest natural cave in the world, hidden deep inside Phong Nha-Kẻ Bàng National Park in Quảng Bình. Reaching it requires an 11km trek through jungle, river crossings, and the remote Bru-Vân Kiều village of Bản Đoòng - with a night camping on a white sandbar inside the cave itself, under a ceiling 145 metres high filled with thousands of nesting swallows.

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 and most historically significant 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 cathedral chambers of ancient stalactites and glowing formations.

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 4-day expedition only, with a strict annual quota of 1,000 visitors, making it one of the most exclusive natural experiences on earth.

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.

Trang An is Vietnam's only UNESCO World Heritage Site recognised for both natural and cultural values - a labyrinth of karst mountains, jade-green rivers, ancient caves, and centuries-old temples navigated entirely by wooden rowboat.

Trung Trang Cave is the largest accessible cave on Cát Bà Island - a 300-metre limestone grotto inside the national park with stalactite formations, a bat colony, and a jungle approach through primary forest.