|Dimension:||A=440 m asl.|
|Guided tours:||self guided|
|As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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The Idagrotte (Ida Grotto) is a huge sandstone cave located at the eastern foot of the Frienstein. It is accesible only on a narrow ledge in the rock face, which requires sure-footedness and a head for heights. We do not recommend visits during bad weather. The ledge is about 50 cm wide and 3.50 m long.
This grotto was used as a cave house during the Middle Ages, the holes for timbers are still visible. The cave was probably a part of the castle on the top of the rock. The summit was used for a watchtower which was also used as an intermediate station in 1410. Later it became the home of robber knights. The cave is first mention by such an robber knight in 1479, who confessed"item beym Freynstein ist eyn loch..., do man die gefangen eynfurt zu peynigen" (at the Freynstein is a hole... where the captured are imprisoned and tortured).
The Idagrotte is rather big, it is formed along a weak horizontal layer of sandstone, so the floor is horizontal and covered by sand. The cave is a through cave and it offers a nice view on both sides. The dry floor and the big size make it a popular campsite and popular for parties. Unfortunately this caused several tragic accidents were drunken sleepers fell down the steep entrance.