E Cave is an active water cave inside Phong Nha-Ke Bang National Park — one of the few caves in the region still entirely untouched by tourist infrastructure. There are no roads leading in. To reach E Cave, you walk 3km through primary jungle in Abandoned Valley from Km19 on the Western Ho Chi Minh Road. Inside, a natural underground river flows year-round from a limestone aquifer, creating the cave’s signature turquoise water — so clear you can see straight to the bottom.

Water temperature inside the cave stays between 18–22°C year-round — noticeably cooler than the jungle outside. This is what makes E Cave different from every other cave in Phong Nha: you don’t walk through it on a boardwalk. You swim or paddle a SUP 1.2–1.5km into the cave, surrounded by 400-million-year-old limestone walls.

Geology

E Cave formed within a limestone massif dating to the Devonian–Carboniferous period, approximately 400 million years ago. The ceiling and walls are densely covered with tetracoral fossils — direct evidence that this entire area once lay beneath an ancient sea.

Inside the cave, tectonic fractures from the limestone mountain-building process are clearly visible. Stalactites and stalagmites have formed slowly over millennia, and flowstone runs in sheets down the cave walls. The cave’s water source originates from Ban Khe Rung at 570m elevation near the Vietnam–Laos border — flowing approximately 35km underground through the Son Doong cave system before emerging at E Cave.

Ecosystem

The entrance of E Cave opens into a wide natural pool — a rich habitat for species characteristic of karst limestone environments: climbing perch, freshwater prawns, and stream fish. If you’re lucky, you may spot the marbled eel (Anguilla marmorata), a species protected under Vietnam’s Red Book, living at depths of up to 20m inside the cave.

The primary forest surrounding E Cave is home to the Ha Tinh langur (Trachypithecus hatinhensis) and the white-cheeked gibbon (Nomascus siki) — two primate species endemic to Phong Nha-Ke Bang National Park. Walk quietly in the early morning and you may hear the gibbons calling from the ridge above.

Explore E Cave with Moc Nam Adventure

Moc Nam Adventure is the only licensed operator for trekking tours into Abandoned Valley — the 2,000-hectare wilderness where E Cave is located. No other company can bring you here. There are currently four itineraries available:

1-Day Tour – Abandoned Valley & E Cave

7.5km trekking through primary jungle, SUP paddle 1.2–1.5km inside E Cave. Suitable from age 5 (dry season, April–August). From $68.25/person.
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1-Day Tour – Golden Cave & E Cave

9km trekking, explore a 3-million-year-old fossil cave with rare 24K gold stalactites, then SUP inside E Cave. Suitable from age 7 (dry season). From $81.90/person.
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2-Day 1-Night Tour – Camping at E Cave

11km trekking, overnight camping at the E Cave basecamp. Wake up to paddle into the cave before any other group arrives. From $156/person.
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2-Day 1-Night Tour – Dark Cave Exit, E Cave & Golden Cave

15km, three cave types in one journey — the most complete exploration of Abandoned Valley. From $226.20/person.
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