Hang Én (swift cave)

Hang Én is a cave on a scale that makes a camping tent look like a grain of rice. A river runs straight through a limestone mountain in the jungle of Phong Nha-Kẻ Bàng National Park in central Vietnam, carving a passage about 1.6 kilometres long whose entrances and chambers rise around 100 metres high or more and widen in places to well over 150 metres. Daylight pours in through the openings onto a broad sandy beach beside a green lake, and the cave is regularly ranked among the largest cave passages on Earth.

The name means "swift cave", after the birds that nest by the thousands on its ceiling and stream in and out of its mouths. The Arem, a small forest people, knew the cave for generations: they sheltered in it on their seasonal journeys and climbed its walls on ladders of branches and vines to take swifts, an important part of their diet. The outside world learned of it only around 1990, when Ho Khanh, a local man searching the forest for fragrant wood, came upon it. In 1994 a joint British and Vietnamese caving expedition surveyed and mapped it.

That survey had a famous sequel. The Rào Thương river disappears underground at the far end of Hang Én and reappears several kilometres away, which told cavers that another great passage had to lie beyond. The search eventually led to Hang Sơn Đoòng, explored in 2009 and now known as the largest cave passage in the world, only a few kilometres away. Expeditions heading for Sơn Đoòng still camp on Hang Én's beach on their way in. In 2014 a Warner Bros. crew filmed scenes here for the fantasy film Pan, released the following year.

The national park around it protects one of the oldest and most extensive karst landscapes in Asia, a forested limestone plateau riddled with caves and underground rivers, and it is a UNESCO World Heritage Site. Hang Én lies in its roadless core. The way in on foot crosses jungle hills and river valleys and passes Bản Đoòng, a tiny village of the Bru-Vân Kiều people, before the first great mouth of the cave opens ahead.

Getting there

The gateway to the national park is the village of Phong Nha on the Son River; the town of Hoàn Lão lies about 30 km from the cave in a straight line. The nearest airport is Dong Hoi Airport (VDH), about 32 km away, and Đồng Hới is also a stop on the North–South Railway between Hanoi and Ho Chi Minh City. From the western branch of the Ho Chi Minh Highway the cave is reached only on foot, by a trek of roughly a day through forest and across rivers.