On the farm of Hellar in Landsveit, this 50m long human-made cave was built up to 11m below the soil at its deepest point. Inside a barn, visitors walk through a secret doorway leading to a dark passage illuminated by lights. Dating back 700 to 1100 years, five ancient chimneys and various carvings remain intact, supposedly made by monks.
The Hellar family believes there are around 170 caves in this area made from sandstone and mud. Their purposes are unknown, but many of them were used at various times to store food. Find Hellnahellir on a dirt road off Rte 26 (where it's signposted). Call ahead to book and get full directions.