Key takeaways
- Thri, hnukar, gigur. Three, peaks, crater. The area is Thrihnukar; the crater is Thrihnukagigur.
- Hard g in the middle and at the end. Icelanders will not mind the attempt.
- In the Blafjoll hills to the south-east, on tarmac most of the way.
- A low scoria cone. Nothing about the outside explains the attention.
Taking the name apart
Icelandic builds long place names out of short ordinary words, which makes them intimidating to look at and straightforward once separated. Thrihnukagigur is three of them stuck together. Thri is three, as in the English three, which it is directly related to. Hnukur is a peak, and hnuka is its plural form in this compound. Gigur is a crater.
So the whole thing is the crater of the three peaks. Written properly in Icelandic it is Thrihnukagigur with accents and a thorn at the front, the letter that gives the th sound in English think, and searchers reasonably type it every possible way.
The three peaks themselves are real and they are the giveaway on the approach: a group of low cones on the lava plain, of which this crater belongs to one. The area is Thrihnukar, plural. The individual crater is Thrihnukagigur, singular. Guides use both and the distinction is genuinely useful once you are out there looking at them.
How to say it
Nobody expects you to get this right, and every guide has heard several hundred versions. As an approximation that will be understood: three-nook-a-gee-gur. The g sounds are hard, as in get, not soft as in gem. The stress lands on the first syllable, which is where Icelandic almost always puts it.
The one sound that is genuinely foreign is the letter at the start, thorn, which is the unvoiced th of think rather than the voiced th of this. If you say the English word three and carry on, you are close enough.
Say it badly and confidently rather than avoiding it. Icelanders are unusually relaxed about foreigners mangling their place names, partly because there is so much mangling to be relaxed about.
The cone from the ridge, with the path running up it
What kind of volcano it is
Thrihnukagigur is a small scoria cone, sometimes called a cinder cone: the kind built quickly by a modest eruption throwing out fragments of frothy lava that pile up around the vent. There are many hundreds of them in Iceland and this one is not distinguished by size, height or shape.
It is part of a volcanic system on the Reykjanes peninsula rift, the belt of activity running south-west from Reykjavik that has been in the news repeatedly in recent years. It last erupted around four thousand years ago and is classed as dormant.
From the rim it looks like what it is. Reddish scoria underfoot, a modest bowl, the lava field it produced spreading out around it, and a hole in the floor of the crater that a person could step over without noticing if it were not fenced and roped.
Everything remarkable about this volcano is below that hole. The cone is a doorway.
The other spellings you will meet
Searching for this place is unusually awkward because it appears under half a dozen forms and none of them is wrong. The Icelandic original uses a thorn at the front and accents on two vowels. English-language operators drop all of that and write Thrihnukagigur. Some drop the h as well.
You will also find it as two words, as Thrihnukagigur Volcano, and simply as Inside the Volcano, which is the name of the visitor operation rather than of the crater. That last one causes real confusion, because it is also a generic phrase that turns up attached to volcanoes in several other countries.
If you are trying to check something specific, the reliable search is the Icelandic spelling plus the word Iceland. The transliterations pull in a startling amount of unrelated material, most of it not in any European language at all.
Three
Thri, hnukar, gigur: three, peaks, crater. The area is Thrihnukar and this crater belongs to one of its cones.
Where it is, and why that matters
The crater sits in Blafjoll, the Blue Mountains, in the hills to the south-east of Reykjavik. The meeting point is a ski cabin called Breidabliksskali, about half an hour from the capital on paved road, and the crater is a further 45 to 50 minutes on foot across lava.
The proximity is the reason this works as a day trip at all, and it is also slightly misleading. Half an hour from a capital city sounds like a suburb. It is not: it is a high, exposed, entirely uninhabited lava plateau that generates its own weather and is regularly in cloud when Reykjavik is in sunshine.
It also means the crater is genuinely close to the airport road and to the Reykjanes peninsula, which is why it fits into an itinerary that most Icelandic day trips do not.
Why anyone has heard of it
Because of what the magma did when the eruption stopped. In almost every volcano on earth the chamber that fed the eruption cools slowly, crystallises and becomes solid rock. Geologists study those as intrusions, exposed millions of years later by erosion.
Here the melt withdrew instead. The chamber emptied, the walls stayed up, and the roof did not fall in. The result is a space about 120 metres deep, narrow at the top and much wider at the bottom, that a person can be lowered into on a platform.
That is the entire basis of the tour, and it is why a small unremarkable cone half an hour from Reykjavik has a steel gantry over it and a booking page. There is no second example anywhere that is open to visitors.
