Off the southeastern coast of Sweden is a small island once known as Blåkulla (Swedish ‘blue hill’). Today the island is known as Blå Jungfrun (Swedish ‘blue maiden/blue virgin’) and is home to a Swedish National Park. In Swedish folklore, the island has had an association with witchcraft since at least the mid-16th century, yet the island may have had a particular folk associations of peculiar danger long prior (a location called “Blaakulla” is referenced in such a manner in 1410—for more on this, see, for example, Stephen Mitchell’s 1997 “Blåkulla and its Antecedents: Transvection and Conventicles in Nordic Witchcraft” in Alvíssmál 7 pp. 81-100).
With that background in mind, a team of archaeologists that have been excavating the site since 2014 have made some interesting assessments of the site, including that the site may have attracted particular religious activity during the Stone Age. According to a recent Livescience article on the topic:
“The results are astonishing and reveal extensive human activities on the island in the Mesolithic Stone Age,” the archaeologists wrote.
People who travelled to the island may have practiced various rituals inside the two caves, archaeologists say. One cave contains what may be an altar where offerings could have been made to deities. Meanwhile another cave has an area that could have been used like a "theater" or "stage."
"In two caves, distinct ritual features were identified," wrote the team members, who hail from Kalmar County Museum and Linnaeus University, both in Sweden.