Gaustad Gruve is a historic iron ore mine located on the east side of Vettakollen mountain in Norway. The mine has operated over the years and re-emerged as a popular tourist destination. Tourists can explore the 70 meter long tunnel from 1804, which was used to drain and move out the ore. It is also home to a large sinkhole that is estimated to be from the 16th century. The site is now protected as a nature reserve full of bats and unique rock formations, making it a fascinating destination for geologists, archeologists and outdoor enthusiasts alike.