Lava Cave.

After we climbed the mountain in the background, we spotted this walking back to the car.

From a distance it looked like a man made structure built up from the lava field, but when we walked closer we found this natural lava cave.

Climbing inside revealed further deep caves and crevasses. The walls looked like dripping melting chocolate since solidified.

The whole thing looks like a big bubble of gas popped through the lava when it was still hot, but it cooled quickly after, taking the shape of the bubble. That's just a guess though!

And this bizzare wilderness is just 20 minutes drive from Reykjavik!