Hang Én, Underground cave system in Quảng Bình Province, Vietnam.
An underground passage stretches 1,600 meters (5,250 feet) through limestone formations, creating multiple large chambers with heights reaching 120 meters (390 feet), traversed by an underground river and sand beaches.
British cavers first mapped the system in 1994 during an expedition through Phong Nha-Ke Bang National Park, documenting geological structures and connections to neighboring caves.
The name references the swiftlets that nest along the rock walls, birds revered in Vietnamese folklore for their speed and ability to navigate darkness.
Access requires a four-hour jungle trek from the nearest road endpoint, with licensed operators offering two-day expeditions that include camping gear and safety equipment, plus overnight stays inside.
Natural light enters through three large collapse openings, allowing tropical vegetation to grow inside, including trees over 30 meters (100 feet) tall that have taken root and flourish.
Location: Quảng Bình
Address: Hang En Cave, Thượng Trạch, Bố Trạch District, Quảng Bình, Vietnam
GPS coordinates: 17.43457,106.30036
Latest update: December 2, 2025 09:33
Caves form through gradual geological processes that can span millions of years. Water dissolves limestone and creates underground chambers filled with stalactites and stalagmites, while ice caves in alpine regions maintain their frozen formations even during summer months. Each cave system tells a distinct story about the forces that shaped it, from chemical erosion to tectonic shifts that exposed new rock layers to underground rivers. This collection includes some of the most geologically significant caves on Earth. Carlsbad Caverns in New Mexico encompasses more than 30 miles (48 kilometers) of passages filled with mineral formations, while Mammoth Cave in Kentucky extends over 400 miles (650 kilometers) through limestone bedrock. Eisriesenwelt in Austria stretches 26 miles (42 kilometers) and contains ice structures that reform each winter. Reed Flute Cave in Guilin showcases limestone formations that began developing 180 million years ago. Waitomo Caves in New Zealand are home to thousands of glowworms that light the darkness with bioluminescence. Puerto Princesa in the Philippines features an underground river that flows 5 miles (8 kilometers) before reaching the sea. Several caves also preserve human history, including Lascaux in France with its 17,000-year-old paintings. These formations demonstrate how water, ice, and time create underground worlds that reveal both geological and cultural history.
Vietnam extends more than 1,000 miles (1,600 kilometers) from mountain regions in the north to the Mekong Delta in the south, offering travelers a wide range of natural and historical sites beyond urban centers. The country includes Buddhist temples like Bai Dinh and Thien Mu Pagoda, cave systems such as Son Doong and Hang En, and rice terraces at Y Ty and Hoang Su Phi. Geographic features span from limestone formations in Ninh Binh to coastal areas at Phu Quoc and Ly Son islands, and waterfalls at Ban Gioc along the Chinese border. Historical sites document different periods of Vietnamese history. The Imperial Citadel of Thang Long in Hanoi preserves royal palace remains, while Po Nagar Cham Towers in Nha Trang date to the 7th century. My Son Sanctuary in Quang Nam holds temple ruins from the Champa civilization, and Cu Chi Tunnels near Ho Chi Minh City served as an underground network during the Vietnam War. The Mekong Delta in the south consists of waterways, floating markets and traditional villages, while Mui Ne sand dunes and Lang Co Beach present different coastal landscapes.
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