Entrance to the Hoverbergsgrottan
The Hoverbergsgrottan (Swedish: Hoverbergsgrottan) is located near Svenstavik in Jämtland on the southern part of Lake Storsjön in Sweden. It was discovered in 1897 by Jöns Väst in the Hoverberg.
The entrance is wedge-shaped and can be accessed via a steel staircase that leads about 12 meters down into a kind of anteroom. From there, another staircase leads down a steep slope into the interior. You enter a cavity that is 20 to 30 meters high. The cave is said to be 170 meters long in total. Parts of the grotto were illuminated with green and red light in early 2010.
Source: Wikipedia