Grjótagjá lava cave

A Water-filled Cave within the Fissure

Grjótagjá lies within the active geological landscape east of Lake Mývatn. The surface is crossed by cracks and fissures associated with the Krafla volcanic system.

The site is commonly described as a small lava cave within one of these fissures. It is neither a long lava tube nor a conventional cavern with a level floor. The visible chamber is irregular, confined and largely occupied by water.

Two low openings lead into the same water-filled chamber. It is possible to climb down through one and leave through the other, but the route is awkward. Visitors must move over uneven rocks, pass beneath a low roof and find secure handholds while remaining clear of the unprotected pool.

The cave is therefore not accessible to everyone. Anyone with limited mobility, poor balance, significant claustrophobia or difficulty bending and climbing should be prepared to remain outside rather than force the descent.

The fissure continues across the surface, and visitors sometimes walk along it while waiting to enter. It is not a separate attraction of equal importance, but it reveals that Grjótagjá belongs to a larger break in the lava rather than being an isolated hole.

The physical surprise is the heart of the place. An unremarkable crack in a rough and apparently dry volcanic surface opens onto clear geothermal water below.

Warm Water and an Older Bathing Tradition

The geothermal water beneath Grjótagjá has attracted people for centuries. Long before the cave became a well-known visitor stop, it was used as a sheltered bathing place.

The name describes the setting. Grjót refers to rock or stones, while gjá means a fissure or rift. Grjótagjá can therefore be understood as the rocky fissure.

Within living memory, people around Mývatn still entered the cave and bathed in its clear warm water. It was possible to visit in this way when today’s older Icelanders were children. That local use matters because the present prohibition can otherwise appear to be an arbitrary restriction placed on a natural pool.

The cave changed. Geothermal activity made the water hotter, while falling rock from the roof altered the physical safety of the chamber. A place remembered as accessible in childhood cannot be assumed to have remained unchanged for decades.

The former bathing tradition should therefore be understood as genuine local history, not as permission waiting to be rediscovered by adventurous visitors. Grjótagjá can now be entered only to view the water.

Jón Markússon and Life beyond the Settled Community

One person traditionally associated with Grjótagjá is Jón Markússon, an outlaw who is reported to have lived in the cave during the early eighteenth century. Accounts of his time there also connect him with bathing in its warm water.

Living in Grjótagjá should not be imagined as a romantic retreat. An outlaw stood outside the ordinary protection of society and depended on whatever shelter, food and assistance could be found. The cave offered concealment and geothermal warmth, but it remained a confined opening in an exposed volcanic landscape.

Jón’s story gives a named person and historical period to Grjótagjá’s older human use. The warm pool was not simply a geological curiosity awaiting modern discovery. It belonged to a landscape local people already knew, used and incorporated into accounts of survival beyond the settled community.

The details of Jón Markússon’s life should be treated as historical tradition rather than a complete documented biography. His association with Grjótagjá nevertheless supports the much broader understanding of the cave as a place of shelter and bathing long before modern tourism.

The Krafla Fires and the End of Bathing

The Krafla Fires were a prolonged period of volcanic and tectonic unrest from 1975 to 1984. They involved repeated magma intrusions, earthquakes, ground movement and eruptions within the Krafla volcanic system.

For people around Mývatn, these events were not distant geological history. They affected familiar land, roads and geothermal features within living memory.

At Grjótagjá, the most direct consequence was a major rise in water temperature. A cave that local people had used for bathing became too hot to enter. Bathing did not resume after the most intense unrest had passed.

The water later cooled, but its present appearance or temperature does not restore its former use. The pool has no supervised access or constructed bathing facilities, geothermal conditions can change, and the landowners prohibit entering the water.

Rockfall from the fractured roof provides a second part of the history. Earthquakes, geothermal alteration, frost and ordinary weathering continue to act upon the lava. No one looking at the calm water can determine that the cave has returned to the condition remembered before the Krafla Fires.

Grjótagjá is therefore a direct example of how people must adapt when an active volcanic and geothermal system changes a place they thought they knew.

Private Land and an Absolute Ban on Bathing

Grjótagjá stands on private land belonging to the farmers at Vogar. Visitors are presently permitted to view the cave, but access depends upon respecting the landowners’ signs and restrictions.

Bathing is forbidden without exception.

The rule applies regardless of how comfortable the water appears, what its temperature may be on a particular day or whether old photographs show people swimming there. The prohibition is not an invitation for each visitor to make an individual safety assessment.

Claims about dangerous accumulations of geothermal gas at Grjótagjá should not be repeated without evidence. They distract from the real situation: the cave has changed, the water was made dangerously hot by geothermal activity, rock has fallen from the roof, the pool is unsupervised and the landowners have prohibited bathing.

Visitors should not test the water from an unstable position or throw stones, coins or other objects into it. Nothing should be left behind, pieces of lava must not be removed and the rock around the openings should not be rearranged.

Continued access depends upon visitors accepting that seeing the pool is the experience now offered. Ignoring the bathing ban risks injury and may threaten future public access to the cave.

Entering a Small and Confined Chamber

Parking is located directly beside Grjótagjá, and the walk to the entrances is very short. That easy approach should not be confused with easy entry.

The descent involves rough, irregular lava. Rocks may be wet, loose or polished by repeated use. The openings are low enough that visitors need to crouch, turn and use their hands. Inside, headroom remains limited, and there is no constructed walkway or protective barrier beside the geothermal water.

The real hazards are visible and physical: an awkward descent, low rock overhead, uneven or loose footing, the history and possibility of rockfall, confined space, congestion and an unprotected drop into the pool.

Grjótagjá becomes crowded quickly. Only a small number of people can occupy the useful standing and sitting areas without obstructing one another. Visitors should wait outside when others are already inside and allow them to climb out before entering.

Moving from one opening to the other is possible but tricky and unsuitable for some visitors. Nobody is required to complete the passage. A person who begins the descent and feels uncertain should turn back.

Large backpacks are best left in the vehicle. They catch against the rock, make turning more difficult and occupy scarce space. Children require close supervision and should enter only if they can safely manage the climb. Dogs should remain outside the chamber.

A Brief Screen Appearance and a Richer Real History

Grjótagjá became internationally recognised through its association with the cave sequence involving Jon Snow and Ygritte in season three of Game of Thrones, in the episode Kissed by Fire.

The real cave helped establish the location, while much of the interior sequence was created under controlled studio conditions. The distinction is easy to understand after entering Grjótagjá. Its actual chamber is small, awkward and too fragile to function like the spacious dramatic interior shown on screen.

The connection is worth mentioning, but it should not dominate the place. Grjótagjá’s genuine history—as a local bathing cave, the reported shelter of an eighteenth-century outlaw and a familiar place transformed by volcanic activity—is considerably richer than its brief screen appearance.

Film fiction also gives no licence to reproduce the scene by entering the water. The landowners’ bathing prohibition applies to every visitor.

Responsible Visiting in an Active Landscape

Grjótagjá can be visited quickly, but patience improves both safety and the experience. If a group is already inside, wait. The water is easier to see, and the cave easier to move through, when people are not trying to pass one another in the confined chamber.

Footwear should grip rough rock securely. Smooth soles are poorly suited to the descent, particularly if the surfaces are damp. Visitors should keep their voices moderate, not to preserve an invented mystical atmosphere but as practical courtesy where sound carries and people need to communicate while climbing.

No candles, smoke or photographic props should be introduced. Food and drinks should remain outside, and nothing should enter the water.

The cave should also be allowed to remain dark. Its character lies in the contrast between fractured black rock and the clear pool illuminated by daylight. Brightening every shadow or flooding the chamber with flash removes the physical experience that makes Grjótagjá distinctive.

The water can genuinely appear blue when daylight enters at the correct angle. Its precise appearance changes with the weather, season and time of day. Visitors should not expect every visit to resemble a heavily processed photograph.

Grjótagjá reveals something broader about the Mývatn landscape. A calm and apparently permanent natural feature can change when volcanic heat, earthquakes and fractured rock alter the system beneath it. Human use must change with it.

• • Grjótagjá is a small lava cave within a fissure northeast of Lake Mývatn.
  • Two low openings lead into the same water-filled chamber, and it is possible—but awkward—to enter through one and leave through the other.
  • Local people once bathed in the cave, but geothermal changes made the water too hot and bathing did not resume.
  • The Krafla Fires were a period of repeated volcanic and tectonic unrest from 1975 to 1984.
  • Jón Markússon, an outlaw of the early eighteenth century, is reported to have lived in Grjótagjá and used its warm water.
  • The cave stands on private land belonging to the farmers at Vogar.
  • Visitors may presently enter to view the water, but bathing is strictly forbidden.
  • The real visitor hazards are awkward footing, low headroom, rockfall history, congestion and an unprotected geothermal pool—not a speculative gas danger.
  • The water can appear vividly blue when daylight enters at the right angle against the dark cave.
  • Grjótagjá is associated with the Jon Snow and Ygritte cave sequence in season three of Game of Thrones, although much of the interior scene was filmed in a studio.