Grjotagja Lava Cave

Grjotagja is a split in the lava field with a chamber underneath and a pool of geothermally heated water at the bottom. The rock is dark, the water is warm rather than hot, and a thin layer of steam sits on the surface. The chamber is small, and there is nothing to do inside but look at the pool. Outside, the ground is split by long fissures, and paths run from the car park across the lava between them.

• The entrance is easy to miss. The cave you see from the car park is sealed with a no-entry sign; the open one is a few metres to its left.
• The path uphill is not the way in. It leads to the rift and to the hiking trails over the lava, not to the cave.
• No facilities. There are no toilets and no drinking water at the site.
• Cramped inside. The chamber is tight; skip it if you are claustrophobic.
• Not for everyone. The way down to the pool is unsuitable for anyone with difficulty walking.

The cave is reached by car, and the car park sits at the site itself, so the last stretch is metres rather than a walk. An information board stands beside the entrance. From there you step down into the chamber over bare lava, and the rock is uneven the whole way.

Better: early morning or late evening. The cave is open around the clock, and in summer there is light in the north of Iceland long into the night.

Avoid: the middle of the day in summer. Only eight to ten people fit in the chamber at once, so a queue builds at the entrance and you wait for it outside.