What is "furillen"

Furillen (older spelling Furilden) is an island in Rute on the northeast coast of Gotland, Sweden. For most of the 20th century, there was a limestone industry on the island until it was closed to the public by the Swedish military in the 1970s–90s, when radar installations became operational. The north part of Furillen is a nature reserve and a Natura 2000 area.