Víðgelmir Cave

Víðgelmir is the largest lava cave in Iceland by volume — a tube nearly a kilometre and a half long in the Hallmundarhraun lava field beyond Húsafell. The surface of a lava river crusted over, the molten rock drained, and the vault it left behind stands higher than a house in places. Inside are colour-streaked walls, fragile lava straws and stone icicles, plus traces of Viking-age visitors on the floor. Entry is by guided tour from the Fljótstunga farm.