Langjökull

Iceland's second-largest glacier (about 950 square kilometres), best known for two activities: the man-made ice tunnel and snowmobile tours. The Into the Glacier tunnel takes you 500 metres into the ice cap through corridors carved into 1,000-year-old ice that glows progressively deeper blue. Tours run year-round (from about 22,000 ISK) and include transport from the Húsafell area in a modified truck.

Snowmobile tours on the surface are the other main draw — you ride across the open ice cap at speed, which is as fun as it sounds. These run from about 25,000 ISK and also depart from the Húsafell area. Both activities take 3-4 hours including transport.

Langjökull is in the western highlands, about 2 hours' drive from Reykjavík to the Húsafell base area. You cannot drive onto the glacier yourself — all access is via tour operators with modified vehicles. The glacier feeds many of west Iceland's rivers, including the ones that supply Hraunfossar and Barnafoss waterfalls nearby.