The Volcano

Þríhnúkar is a safely dormant volcano that has erupted three times. The last eruption, which took place about 4,500 years ago, left behind a unique natural phenomena: Þríhnúkagígur "Three peak crater". It is truly one of a kind and the only accessible lava chamber on Earth. Inside, the beautiful coloration and unique rock formations represent all the shades and shapes of the earth where its size is enormous and to some extent intimidating.

Last eruption

4500 years ago

Thrihnukagigur volcano is safely dormant

Crater depth

Total depth is 212 m (700 ft)

You can easily fit the Statue of Liberty in there!

Ground space

Ground floor is 50x65 m (160x220 ft)

Make no mistake - it’s huge!

Age limit

8 years old minimum age

Small feet that can cover the 3,5 km each way in all weathers are always welcome.


Þríhnúkar (Three Peaks) formed in three separate volcanic eruptions. The peaks line up within a few hundred meters of each other so they can be clearly distinguished from afar, hence the name. The three peaks reach an elevation of about 550 meters and are of nearly the same height.

The most northeasterly one, Þríhnúkagígur is the youngest and is considered the most important volcano speleological phenomenon on Earth. The name applies to both the outside and the inside of the 35m high cinder cone, which formed in an eruption about 4.500 years ago. There is a funnel shaped opening on top of the cone leading into the almost 200 m deep open vertical volcanic conduit, the plumbing system of the volcano. The bottom originates from around the time that modern humans first walked the planet, about 30–40.000 years ago. The crater walls tell the story of all the local geological processes that have taken place since then. The unexpectedly diverse microbial life offers clues about the development of life on Earth, and even on other planets. The crater is not only the third largest in the world, but also the deepest formation of its kind.

The middle peak, a scoria cone, is located 200 m west of Þríhnúkagígur. It stems from an older Þríhnúkar eruption, which took place about 500 years earlier. It is a part of an elongated shield volcano crater, which is now half-filled with the younger Þríhnúkar lava. The tidal level of the absolutely flat secondary lava pond can be seen around most of the circumference of the rim.

The third peak, furthest to the west, consists of hyaloclastite, a rock typical of having been quenched in contact with ice and water. It formed in a subglacial eruption, deep within the glacier, more than 50.000 years ago. At the time, most of Iceland was covered with a thick ice cap. We are talking about ice age here!

The heart of the volcano

The magma chamber is often referred to as the heart of the volcano. It’s there that the liquid rock waited to find a way through to the surface, causing a volcanic eruption.

Usually, when an eruption ends, the lava chamber inside a volcano solidifies. Þríhnúkagígur volcano is a rare exception to that nature, as the magma in the chamber seems to have disappeared after the eruption. It’s believed that the magma retreated to the depths of the earth. Haraldur Sigurdsson, volcanologist, explains it like this:

“Þríhnúkagígur is unique (…) It’s like somebody came and pulled the plug and all the magma ran down out of it.”

Why it survived remains a mystery.

Years of Exploring

On a bright winter day in 1974 the cave explorer Árni B. Stefánsson became the first human being to enter Þríhnúkagígur. He was lowered in by a few of his friends in an adventurous exploration of the phenomenon.

It wasn't until 1991 that his brother Einar and Einar's friend; Björn Ólafsson, started to explore the cave, making several expeditions with Árni, where they made daring attempts to map out the gigantic cavern inside the volcano. For years they went down, in ropes, hanging in their harnesses with headlamps, slings and belay devices. Slowly the idea came up to make it accessible to the public and in 2004 Árni presented the first idea of making a tunnel into the chamber.

In year 2010 an expedition from National Geographic came for filming inside the volcano. It was a big operation that needed different approach than to use climbing ropes to get in and out. The founders started to devise how to lower people and equipment into the volcano. The solution was to use a heavily modified window cleaning lift. It worked like a charm and since 2012 people are now able to go inside the volcano to experience mother nature in all its magnificent grace.


Simply put, Iceland is one giant geological hotspot. The country is one of the most active volcanic regions in the world, with eruptions occurring every 3–4 years on average. But why is Iceland so active? It’s mostly due to its location on the Mid-Atlantic Ridge, where the Eurasian and North American plates are moving apart – and therefore literally opening the earth’s crust. In the center of this ridge sits Þríhnúkagígur volcano.

Despite of all this activity, there are no indications of Þríhnúkagígur erupting again in the near future.

The three craters (one of which you will be descending into) are prominent landmarks, standing against the sky on the highland edge, about 20 km (13 miles) southeast of the capital area, within the protected area of Bláfjöll Country Park.

It´s HUGE!

The peak you will enter is a small cinder cone, standing about 35 m (100 ft ) higher than its surroundings. At the top of this cone is a funnel-shaped opening, about 4×4 m (12×12 ft) wide entrance of a huge 120 m (400 ft) deep, bottle-shaped volcanic vault. The bottom measures 50×70 m (160×220 ft). Volcanic passages continues down to the southwest, to a total depth of about 200 m (700 ft).

The beauty of the crater mostly consists in the various coloration found inside it, and its enormous and to some extent, intimidating size. To put it in context, the ground space is equivalent to almost three full-sized basketball courts planted next to each other and the height is such that it would easily fit a full sized Statue of Liberty into the chamber. So make no mistake – it’s huge!

How it is done

We have an innovative method to lower visitors down through the crater’s opening. Based on a system used to carry window cleaners on the side of skyscrapers, we custom built our volcano lift and employ it to lower our guests into the volcano.

Basically, it's a basket that holds 7-8 people. It is connected to a crane that has been placed vertically over the crater opening. Massive cable wires safely move the basket up and down the bottle-shaped vault, from the crater's edge and all the way down 120 m (390 ft) to the bottom.

Several guides, all highly trained and experienced, are by your side at all times, making sure everything runs smoothly and safely.


At the base of the volcano you find our cozy Base Camp. This is where guests are geared up and get served coffee, tea or hot chocolate and of course our famous 'all you can eat' Icelandic lamb or vegetable soup. This is a particularly nice feature when the weather is not in our favor.

Base Camp is located in the middle of the water reservation area for the capital. That is why it is totally forbidden to drive to the camp. The camp were brought in by helicopter, just like everything else on location that’s too heavy for human transport. This includes the elevator that is brought in every spring and removed every autumn. The meat for the soup has even gotten a ride in a helicopter when the bulk is too heavy for our guides to carry it.

Base Camp also provides most of the necessities required for a day in the wilderness, including restrooms and a wireless internet connection. You will find peace and warmth and meet a lot of new people from all around the world.

The Lava Shop

Base Camp is the only place on Earth where you can buy Inside the Volcano products and souvenirs. There you can buy some practical things like gloves, hats or even sweaters. This can come in handy when the weather makes its typical Icelandic sudden shifts. The sweaters bears the logo of the tour, making it the perfect souvenirs. They are still our most popular item in the shop. Our favorite things though, are our new cups, they come in our colours and tell our mantras, like „Are you a volcano? because I lava you“ or „Crater coffee“ ... Ok, ok, you will understand this you see it.

Book the Tour

You can book your tour now in few easy steps. You select your date, decide how many you are and with your credit card you can confirm your booking. Yes, your adventure is just one click away.

Video of the tour

This could be you!