As lava is porous, rainwater seeps easily through its layers and does not run on the surface.
This makes it difficult to find drinking water in areas covered with lava. Vatnshellir ‘Water Caves’ are lava tubes, formed when a channel of molten lava flowing from a crater or fissure emptied at the end of an eruption, leaving a tunnel-shaped cave behind.
The Vatnshellir caves are about 200m long and formed about 5000-8000 years ago.
Descending by a spiral staircase into the cave, it’s fascinating to see what the lava field looks like on the inside.
There are stalactite formations that have grown over thousands of years and bacterial growth that reflects on the walls and ceiling of the caves.
The caves are only open to visitors on guided tours (free for children 11 years and younger) and you'll be provided with a helmet and headlight.
Good walking shoes and warm clothing are necessary as well as gloves as it is cold inside the cave.
Vatnshellir caves are by road 574, a 10-minute drive from Hellnar and tours run year-round by arrangement.