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:

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.

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

Why visit Sơn Đoòng Cave Expedition

Sơn Đoòng is a once-in-a-lifetime experience — entering the world's largest cave is genuinely transformative, with those two dramatic jungle-filled dolines and the 200m cathedral chamber unlike anywhere else. The expedition is expertly managed by Oxalis, with guides who understand cave geology and jungle ecosystems, and the trekker cap (≈1,000 per year) means you're not jammed in with crowds. If you have 4 days and $3,000, this is the most extraordinary immersion available in Southeast Asian wilderness.

When to go

The cave is only open January through August; September–December flooding makes it unsafe. March to May delivers the best window — cool dry weather, stable jungle humidity, and predictable water levels — though April can attract peak bookings. July–August are quieter but still operationally reliable, with marginally higher humidity. Avoid the monsoon months (September–November) entirely unless Oxalis confirms unusual dry conditions.

How to get there

Fly from Hanoi or HCMC to Đồng Hới airport (Vietnam Airlines, VietJet, Bamboo; ~3 hours from Hanoi, 2.5 from HCMC, typically 1.8–2.2 million VND / $72–88). From Đồng Hới, Oxalis arranges a 50 km transfer to Phong Nha town (included in the $3,000); the drive is 1.5–2 hours. See Phong Nha town for accommodation the night before departure.

What to see and do

• Garden of Edam: A full rainforest thriving inside the cave under a collapse doline — trees, vines, and light cones at midday create an ethereal jungle cathedral.
• Great Wall of Vietnam: A 90m flowstone barrier you ascend via safety ropes and fixed ladders — dramatic vertical climbing inside a cave.
• Doline light shows: The "Watch Out for Dinosaurs" doline floods the cave with noon light; bring a camera for those golden-hour shots.
• Underground river and fossils: Wade through icy cave streams, spot 2-million-year-old fossils embedded in limestone, and keep an eye for cave-adapted blind fish and transparent shrimp.
• Sand bank camps: Sleep under open sky inside the cave on Days 2–3 — a surreal experience with the cave ceiling as your stars.

Where to stay nearby

In Phong Nha town, budget options like Jungle Boss or Phong Nha Central (350–500k VND / $14–20) cater to backpackers. Mid-range includes Phong Nha Riverside Boutique and Phong Nha Discovery (900k–1.5M VND / $36–60), with riverside views and river adventure packages. Premium is Tam Coc Gardens Hang Múa (1.8–2.5M VND / $72–100), a 45-minute drive toward Tam Cốc. Oxalis includes one pre-expedition night; book additional nights separately if acclimatizing.

Practicalities

• Entry fee / hours: $3,000 per person (2026 rate), January–August only. Park entry permits included.
• Fitness and safety: You must walk 10–15 km daily over rocky terrain, climb on safety ropes, and swim — Oxalis screens all trekkers; age 16–70 typically, though fit exceptions are made. The cave is cold (≈18°C) and damp; bring the provided wet gear and underestimate nothing.
• Foreigner pitfall: Many travelers underestimate fitness or arrive with insufficient conditioning; Oxalis will refuse entry on the day if you cannot safely complete the ascents. Train legs, cardio, and grip strength weeks before booking — don't gamble on a $3,000 deposit.