Surtshedlir Cave

Past the first entrance the light stops. Surtshedlir is a lava tube left by a volcanic eruption, the longest in Iceland, with ice stalagmites and archaeological remains inside. Nothing is lit, paved or fenced. The floor is loose lava blocks, and you climb over them rather than walk along. A couple of hundred metres in, the darkness is total. Comparable caves elsewhere in Iceland are sold as guided tours on lit walkways. This one is entered on your own, through numbered openings in the surrounding lava field.

• Bring a headtorch: A phone light shows where you step, no more. Past the first chamber the cave is completely dark.
• Dress for the cold: It is cold in the tunnel and windy outside. Wear warm layers, stiff boots and clothes you do not mind tearing.
• No facilities: There are no toilets at the cave. Nothing inside is lit, railed or signposted.
• Know your exit: Openings 2 and 3 have no way out. After them the next exit is opening 4.
• With children: The traverse can be done with young children, but it is slow going over broken rock.

The last stretch is gravel: about 15 minutes of driving, ending at a parking area roughly 400 metres from the cave. Road signs call for a 4x4. In dry conditions two-wheel-drive cars have made it, driven slowly. In February the road stays open with snow lying across the whole area. From the parking the walk to the entrances crosses open lava. The exits further along the tunnel come out on the same lava field, and the walk back to the car from there is short.

Better: summer and dry weather. The gravel road is then passable in a two-wheel-drive car, and the lava between the openings is clear.

Avoid: winter without a 4x4. In February snow covers the whole area, and the route between the openings has to be broken through it. Inside the tunnel it is cold and dark in any season, so the time of year changes the approach, not the cave.