Stalactite cave on Flickr.
The Saalfeld Fairy Grottoes (German: Feengrotten) are the “most colourful grottoes in the world” (Guinness Book of Records). The grottoes are situated near Saalfeld in Thuringia, Germany. They were originally mines, and at one point were named Jeremia’s Luck. At the Fairy Grottoes, you can take three different tours. (taken from en.wikipedia.org/wiki/Saalfeld_Fairy_Grottoes)