Mýrdalsjökull

Where it sits. Mýrdalsjökull is Iceland's fourth-largest ice cap, covering roughly 590 square kilometres of the southern highlands directly north of Vík í Mýrdal. Its ice reaches around 750 metres thick in places and its highest points stand near 1,490 metres. Route 1 runs along its southern margin, so the cap is visible from the road for 60 kilometres, and several of its outlet glaciers push down close enough to the ring road to be reached on a short side trip. To the west it nearly touches Eyjafjallajökull, separated only by the Fimmvörðuháls pass; to the north the highland tracks of Emstrur and the Laugavegur trail skirt its edge.

What is underneath the ice. The cap sits on Katla, one of Iceland's most dangerous volcanoes, whose caldera is about ten kilometres across and buried beneath several hundred metres of ice. Katla has erupted around twenty times since settlement, on a historical average of roughly twice a century, with the last unambiguous eruption in 1918. The threat is meltwater: an eruption beneath the ice generates a jökulhlaup, a flood of water, ice blocks and sediment that can reach discharges comparable to the largest rivers on Earth for a few hours. The 1918 flood pushed the coastline south of the cap several kilometres out to sea with deposited sediment. The volcano is closely monitored, and the seismic and GPS record is public.

The outlet glaciers. Sólheimajökull is the accessible one: a tongue that reaches down to about 100 metres above sea level, signposted from Route 1 along Route 221, with a car park and a 1.5-kilometre walking track to the ice front. It has retreated dramatically — hundreds of metres within recent memory — and a proglacial lake now sits where walkers used to step straight onto ice, which makes it a blunt teaching exhibit for glacial retreat. The ice at the tongue is striped with dark bands, each one an ash layer from a past eruption of Katla or Eyjafjallajökull, so a guide can point out individual years in the wall of a crevasse. Guided walks with crampons run daily year round from the car park. Kötlujökull, on the eastern side above Mýrdalssandur, is the ash-blackened tongue where the Katla ice cave is reached by modified vehicles from Vík, one of the few ice caves in Iceland accessible in summer as well as winter. Entujökull and Sléttjökull face the northern highlands.

On screen. The southern ice caps supplied Game of Thrones with the lands beyond the Wall. The second season's Frostfangs and Fist of the First Men sequences, with Jon Snow, Qhorin Halfhand and the Night's Watch ranging party, were shot on Icelandic glacier terrain in late 2011 and early 2012, and the district around Mýrdalsjökull and the Vík heathlands carried a share of that work along with the larger outlets of Vatnajökull further east. The seventh season returned to the same region in the winter of 2016 and 2017 for the wight hunt. Snowmobile and super-jeep operators on Mýrdalsjökull have run location-themed trips ever since, and the ice cap also appears regularly in car advertising and in feature work needing a convincing polar surface within three hours of Reykjavik.

What a visit actually involves. Nothing here is a walk-up sight. The ice cap surface is reached by snowmobile or modified vehicle from a base on Route 222, and the tours are weather-dependent and cancelled often in winter. Glacier walks on Sólheimajökull require a guide, crampons and a helmet, and unguided access onto the ice is genuinely dangerous: the surface is riddled with crevasses and moulins, the tongue calves into its lagoon, and the moraine is unstable. The Katla ice cave trip from Vík runs three to four hours including transfer. For those who want the cap without paying for a tour, the Sólheimajökull viewpoint path and the pull-offs on Route 1 near Pétursey give a sense of the scale for free.

Getting there and timing. The Sólheimajökull turn-off is about 160 kilometres from Reykjavik, roughly ten minutes west of Vík, and Route 221 is a short gravel road passable in a normal car in summer. Winter conditions on the ring road here vary hour to hour; the Icelandic road authority publishes live status, and the stretch across Mýrdalssandur closes in high wind. Ice caves are naturally a cold-season activity in most of Iceland, but Kötlujökull's cave is a summer option too. Bring layers, waterproofs and boots that take crampons, and accept that a booked glacier day may be moved or refunded — on a volcano covered in ice, the weather has the final say. The 2010 eruption of Eyjafjallajökull, on the neighbouring ice cap, closed roads across this district for weeks and left ash that still lifts into the air in a dry easterly wind.