Key takeaways
- On a rope, by an Icelandic caver, into a shaft nobody had been down.
- A known hole is not the same as an accessible one.
- The lift, the gantry and the tours date from the 2010s, not from the discovery.
- A short season, small parties, and a walk that filters the numbers.
A known hole nobody had entered
Iceland is not short of holes. The lava fields around Reykjavik are riddled with fissures, tubes and collapses, and the ones near a ski area half an hour from the capital are not exactly secret. Thrihnukagigur's opening was known long before anyone went down it.
Knowing about a hole and getting into it are different problems. This one is a vertical shaft in the floor of a crater, on an exposed lava plateau, in a country with a short workable season and abundant weather. Descending it requires rope, competence and a reason.
The reason, when it came, was caving rather than science or tourism. Iceland has a small and serious caving community, and vertical shafts are what that community exists to descend.
1974
The first descent was made in 1974, on a rope, by the Icelandic caver Arni B. Stefansson. He went down the shaft expecting what you would expect: a shaft. What he found was that the walls stopped being close to him.
That is the moment the story turns on. A vertical shaft in a lava field is an ordinary object. A shaft that opens out below into a chamber the size of this one is not, and the recognition that this was the volcano's own magma reservoir rather than a drained tube is what gave the place its significance.
He returned, and he spent a great deal of the following decades arguing for the site: for its protection, for its study, and eventually for a way to let other people see it. It is not a common thing for the first person into a cave to still be shaping what happens to it forty years later.
The steel gantry spanning the crater mouth
From rope to platform
For a long time after 1974 the only way in remained the only way in. Cavers went down; almost nobody else did. A rope descent of 120 metres is not a thing you can offer to a coach party, and any proposal to widen access ran into two hard constraints at once.
The first was engineering. You cannot put a staircase into a chamber like this without wrecking exactly what people would be coming to see, and you cannot enlarge the opening without changing the object. Whatever went in had to be light, removable and hung from above.
The second was preservation. This is a scientifically valuable and physically fragile place, four thousand years undisturbed, with mineral coatings on the walls that a careless hand removes permanently. Any access scheme that damaged it would have destroyed the reason for the access.
The answer was a steel gantry spanning the crater mouth with an open platform suspended beneath it, lowered on a winch. It touches almost nothing. It goes down through the existing opening without widening it, it carries a handful of people at a time, and it can be taken out. Public tours followed in the 2010s.
The compromise shows in the numbers. Small parties, a fixed schedule, and a season that closes when the weather does.
What was at the crater before the gantry
It is worth picturing the site as it was, because almost nothing is there now either. There is no visitor centre, no car park at the crater, no road to it. What exists is a path across the lava, a fenced opening, a steel span, and a hut back at the treeline where the soup is made.
Everything else is seasonal. The gantry and the platform are the permanent structures; the rest of the operation arrives at the start of the season and leaves at the end of it. That is why photographs taken in different years look so consistent: there is very little to change.
The interpretive boards at the crater are the only concession to a visitor centre, and one of them is a geology panel credited to two named Icelandic geologists rather than to a tourism department. It is a small detail and it tells you what kind of site this is: scientific first, and commercial second, in that order and by some distance.
1974
The year of the first descent, on a rope, by an Icelandic caver. Public access followed decades later, on a platform hung through the same unwidened opening.
Why access is still deliberately small
It would be straightforward to move more people through this crater. Widen the path, run more departures, put a bigger platform in, sell the descent as an attraction rather than an expedition. None of that has happened, and the constraints are not accidental.
The walk is the first filter and it is a real one. Forty-five to fifty minutes each way over uneven lava removes a substantial fraction of the people who would otherwise book, which is one reason the operator states its unsuitability for mobility impairments plainly rather than burying it.
The party size is the second. Four or five people descend at a time, which sets a hard ceiling on throughput no matter how many departures run. It also produces the experience people describe afterwards, which is closer to being shown something than to visiting an attraction.
And the season is the third. This is a high exposed plateau in the North Atlantic. For a large part of the year getting a group across the lava safely is not a reasonable proposition, and the operation stops rather than pushing it.
The result is a site that has been open to the public for over a decade and still feels like it has barely been visited, which is unusual enough to be worth protecting.
