Photo: Entering the cave by boat.

Dark Cave (Hang Toi)

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Hang Toi, more commonly known as Dark Cave, has been tweaked to appeal to adventure seekers. Despite all the added artificial frills such as arriving to the entrance via Vietnam’s longest zip-line, the main attraction is venturing into the cave with just headtorches and plunging into a narrow cavern full of thick, wonderfully gloppy, gooey mud. “Dark” may refer to the unlit cave itself or your body after the mud bath. Either way, prepare to get dirty and have some primitive fun.

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Heigh-ho, heigh ho, it's off to mud we go.

Heigh-ho, heigh ho, it’s off to mud we go.

The six kilometre Dark Cave is located within Phong Nha-Ke Bang National Park. The main entrance is on Ho Chi Minh Highway West, about five kilometres north of Paradise Cave. Unlike Paradise Cave, which is artificially lit and is about politely observing the interior from a fenced boardwalk, Dark Cave is about plunging in. It has been developed into a backpacker playground, as evidenced by the 400-metre zip-line to the entrance of the cave.

Zipping and caving.

Zipping and caving.

Once inside the cave, switch on the light on your miner helmet for a barefoot walk through a crevasse that gets narrower and narrower, muddier and muddier until it is walls of thick clay to each side and underfoot. Eventually there is no trail, just deep footprints left from the person in front. Every step (and misstep) becomes a comical struggle of squelching for 300 metres. If you get claustrophobic, Dark Cave is not for you.

Finally the crevasse widens into one big mud pit.

The mud is remarkable. It has the consistency and colour of a rich chocolate milk, and it’s buoyant – you cannot sink. You’ll effortlessly float like a cork in the Dead Sea. You’ll bob up and down and roll around and around. Even trying to set your legs down is almost impossible.

After de-mudding with an invigorating swim in the cave’s crisp, cold river (in pitch darkness, mind you), you’ll head back with kayaks. To add to the spectacle, they’ve set up an obstacle course over the water and a flying fox which attracts backpackers like bees to honey. On hot days you’ll find yourself lingering here, taking cooling dips in the green-blue Chay River.

Hang in there.

Hang in there.

The pricing system is more complex than it should be. The entrance fee is 80,000 dong per person, but you only get access to the first 150 metres of the cave. To get there and back, you’ll need a kayak, 10,000 dong per person. For the mud bath you need a guide: the “regular access tour” which includes zip-line there, mud and kayak back is 270,000 dong per person, 170,000 dong in the rainy/cold season (September to March).

And behold, the “full access tour fee” which adds activities on the Chay River. It’s 450,000 dong per person, 250,000 dong in rainy/cold season.

Front crawl, dark cave.

Front crawl, dark cave.

A park tour is an easy way to cover several sights in one day. Phong Nha Discovery offers the National Park Tour, a guided day trip which includes Paradise Cave, a War Martyrs Memorial, in addition to Dave Cave, lunch, transport and admission fees. Cost is 1,350,000 dong per person, from 08:30-17:30. Book the tour through Phong Nha Farmstay, Easy Tiger Hostel or Phong Nha Discovery (office based in Dong Hoi at 63 Ly Thuong Kiet Street; T: (052) 3851 660;;

If you are doing it yourself, tours arrive in the afternoon so it will be quieter in the morning. However, there has to be four or more people before they take you in, so you may have to wait.

There are lockers, a restaurant and a small change room. DO NOT take anything valuable into the cave – the mud will take it. DO NOT submerge your head under, you’ll be digging out mud from your orifices for years. Wear dark swimwear (anything light will stain). And take it from our personal experience, thoroughly wash and dry your swimsuit immediately after the trip, or else it will stink!

Add underground mud bath to your bucket list.

Add underground mud bath to your bucket list.

For a different side of the cave, literally speaking, the Abandoned Valley Jungle Trek explores Thuy Cung Cave, the other end of Dark Cave. The one-day trek descends and ascends the valley traversing jungle and many rivers, so you’ll need to be relatively fit and need proper attire including long trousers. The full-day trip costs 1,500,000 per person, minimum two people. You can book it through Jungle Boss Homestay.

Except for the shot of the zip-line sign, pictures were taken by Phong Nha Discovery as part of the trip service.

What next?

 Browse our independent reviews of places to stay in and around Phong Nha.
 Check prices, availability & reviews on Agoda or Booking
 Check out our listings of things to do in and around Phong Nha.
 Read up on how to get to Phong Nha, or book your transport online with Baolau.
 Do you have travel insurance yet? If not, find out why you need it.
 Planning on riding a scooter in Phong Nha? Please read this.
 Browse the web securely while travelling with TunnelBear. Try with a 7–day free trial.

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Where to next?

Where are you planning on heading to after Phong Nha? Here are some spots commonly visited from here, or click here to see a full destination list for Vietnam.

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