Askja

Askja is a caldera set inside the Dyngjufjoll mountains in the empty interior north of Vatnajokull, surrounded by tens of kilometres of black ash and lava in every direction. Inside it lies Oskjuvatn, a very deep lake formed after a major eruption in 1875, and beside it Viti, a smaller explosion crater holding milky blue-green geothermal water. The drive in crosses unbridged rivers and pumice desert, and the final approach is a walk of about 2.5 km over lava and old snowfields. Bathing in Viti has been restricted at times because the crater walls are unstable, so check the current situation locally rather than assuming you can swim.

What you actually see

• Oskjuvatn - the dark caldera lake, still ice-covered into summer in some years.
• Viti - the smaller crater below the rim with pale blue-green water.
• The ash desert - the approach across pumice and lava with no vegetation at all.
• Drekagil - the gorge and hut at the road end, the usual base for the walk in.

When to go

The tracks usually open in July and close with the first serious snow in September, and the exact dates vary each year. Go on a clear day; in cloud the caldera is a grey bowl with nothing visible. Start early, because the driving alone takes several hours each way from Myvatn or Egilsstadir.

Honest expectations

This is a long, rough day. The highland tracks demand a high-clearance 4x4 and river-crossing experience, and there is no fuel, phone signal or help for hours in any direction. The final walk crosses snow patches into September. Viti is often closed to bathers, and the lake is bleak rather than pretty in poor light.

Nearby

Myvatn and the Herdubreid massif lie to the north, and the tracks continue into the interior.