Balls of mist roll like tumbleweed around crater rims, whipped up by howling winds charging at 15 metres per second.
Struggling to hold my balance, I almost have to crawl on my hands and knees. The fact I’m dressed only in a bikini doesn’t really help matters.
It might sound like insanity, but I’ve come to this remote, sparsely-populated region of northern Iceland to go swimming.
A natural lagoon with 40 degree water heated by geothermal energy, the Myvatn Nature Baths opened to the public in 2004.
Less commercial than the Blue Lagoon in the south of the island — now replete with floating bars, spa robes and mud-pack dispensers — this mineral-rich hot spring offers a much simpler and wilder alternative.
Reached by a short flight from Reykjavik to Iceland’s second city Akureyri, this wild and rugged region is attracting an increasing number of tourists, lured by other-planetary scenery, geological phenomena and the promise of being one of the best places in Iceland to the see the Northern Lights.
‘This is a town of trees,’ says my guide Siggi, whose family have lived in this area since the 17th century.
‘There are trees in every backyard and some people even own volcanoes,’ says Siggi, a former farmer with a wry sense of humour, who speaks in gruff Norse tones through a beard of wiry ginger hair.
‘My family have two mountains,’ he adds.
Even on nights of low activity, it’s possible to see the Northern Lights rippling across the sky, and no matter how cloudy it is, there’s always a patch of clear sky above Lake Myvatn.
We drive to Dimmuborgir, a ridge of craggy lava formations, where shapes and shadows fuel imagination, and irregular pillars are said to be trolls turned to stone by the sun.
I stay up until 3am chasing the lights, long after the full moon has rolled below the horizon, yet the best display is behind my hotel, overlooking Lake Myvatn, where reflections arch and spiral across the water.
But north Iceland’s best sights are not just overhead - there’s also plenty to explore below the earth’s surface.
Lefthellir lava cave was formed by an explosion of blazing hot lava 3-4,000 years ago, but now temperatures have dropped it’s filled with impressive ice sculptures - jagged monoliths rising from the cave floor.
First spotted by a farmer in 1982, the cave is well camouflaged by spools of rope lava which wind tightly around the landscape, and getting inside isn’t easy: the narrow entrance is a hole just 50cm high and 1m wide.
I wriggle like a worm to squeeze through, losing buttons from my jacket.
‘We once had a woman whose chest was so big she got stuck,’ laughs our cave guide Oli. ‘We had to undo her bra strap so she could get through.’
But the sweat, tears and lost garments are worth it.
We spend two hours exploring the different levels, using ropes to slide down frozen ridges and playing music by chiming blocks of ice.
Before leaving, Oli instructs us to switch off our headlamps.
I wait for my eyes to grow accustomed to the darkness but they never do. Only the dripping sound of melting ice water grows louder.
Deep below the earth’s surface, I’m playing out my dreams.
Regent Holidays (regentholidays.co.uk) offer a Nature Break from £360, including three nights’ accommodation at the 4-star Hotel Reynihlid and entrance to Myvatn Nature Baths. Add return international flights with WOW Air, airport transfers, one night at the 4-star Icelandair Hotel Reykjavik Marina and internal flights Reykjavik-Akureyri with AirIceland for an additional £790.
WOW Air (wowair.co.uk) flies to Reykjavik from London Gatwick from £74 one-way.