Sơn Đoòng Cave Expedition

Sơn Đoòng is the largest cave in the world by volume — 38.5 million cubic metres, big enough to fit a 40-storey skyscraper. Found by a local farmer in 1990 and explored by British cavers in 2009, it has been open to commercial expeditions since 2013 under a single permit holder.

What it is

A river cave inside Phong Nha–Kẻ Bàng National Park, 5.4 km long, with two collapse dolines that allow jungle to grow inside it. The largest chamber is 200 m tall and 150 m wide. Entry numbers are capped at around 1,000 visitors per year by Quảng Bình province; permits are held exclusively by Oxalis Adventure (oxalisadventure.com).

The expedition

A 4-day, 3-night itinerary running January through August only:

Day	Route	Notes
Day 1	Phong Nha to Hang Én via 10 km jungle hike	Camp inside Hang Én
Day 2	Hang Én to Sơn Đoòng entrance + first chamber	Camp 1 inside Sơn Đoòng
Day 3	Through Sơn Đoòng to Camp 2 by Garden of Edam	Climb up to "Great Wall of Vietnam" optional
Day 4	Exit via Sơn Đoòng's second doline, return to Phong Nha	Long day, vertical rope ascent

The route involves swimming through rivers, climbing the 90 m "Great Wall of Vietnam" (a flowstone barrier), and via-ferrata sections. You sleep in expedition tents on sand banks inside the cave.

What you see

• The Garden of Edam — a rainforest growing inside the cave under the second doline.
• The Watch Out for Dinosaurs doline — first doline, with light cones at midday.
• Stalagmites the size of houses (some 70 m+).
• 2-million-year-old fossils embedded in the walls.
• Cave pearls in the underground river.
• Unique cave-adapted ecosystem — blind fish, transparent shrimp.

How to get there

You fly or train to Đồng Hới, then transfer to Phong Nha town (50 km) where Oxalis is based. The expedition meets at the Oxalis base in Phong Nha for a full briefing the day before departure. Vietnam Airlines, VietJet and Bamboo all fly Đồng Hới from Hanoi and HCMC.

When to go

January to August only. The cave's underground rivers flood in the September–December monsoon and the cave is closed for safety. The driest, most stable weather is March to May.

Cost and what's included

The 2026 price is $3,000 per person. Included:

• All meals from Day 1 lunch to Day 4 lunch.
• Camping gear, sleeping bags, safety gear, helmets.
• Porters (around 25 per group of 10 trekkers).
• Two safety officers per expedition.
• Park entry permits.
• One night's accommodation in Phong Nha before the trip.
• Transfers from/to Phong Nha town.

Not included: international flights, Đồng Hới flights, tips for porters and guides (~$80 total per trekker).

Fitness requirements and screening

You must be able to walk 10 km on uneven ground for several consecutive days, climb a 90 m wall on safety rope, and swim a short stretch. Oxalis requires a self-declared fitness assessment at booking and reserves the right to refuse entry if you cannot meet the requirements. Age range typically 16–70 but they make exceptions either side for clearly fit trekkers.

Booking timeline

Bookings open annually for the next year, usually around October. Popular months (March–May) sell out within hours. Quieter months (July–August) may have availability into the same year. There is no waiting list — book the moment slots open.

Practicalities

• The pre-trip kit list is long and Oxalis provides almost everything technical.
• Photography is allowed (and encouraged) but no commercial drones inside the cave.
• Mobile signal is absent for the entire trip.
• One group of up to 10 trekkers per expedition.
• Tipping porters is the right thing — they carry your food on bamboo poles.

Honest take

Sơn Đoòng is the most extraordinary single experience in Vietnam if you can afford it and you are fit. It is genuinely unique — there is no equivalent commercial cave trip anywhere on Earth — and Oxalis runs it with rare professionalism. The conservation-focused permit model and the trekker cap mean the experience has not been degraded by overuse.

If $3,000 + flights is too much, do Hang Én at $370 — you camp in the same cave Sơn Đoòng trekkers use on Day 1, and you get 70% of the visual impact. That is the smart compromise pick.

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Related: Hang Én cave · Phong Nha–Kẻ Bàng NP · Paradise & Phong Nha caves · Phong Nha town