The Saalfeld Fairy Grottoes are caverns or grottoes of a former mine in near Saalfeld, in the German state of Thuringia. They have long been famous for their countless colorful mineral formations (speleothems) formed over many years by water dripping through relatively soft rock. Since 1993, the Guinness Book of World Records has termed the Feengrotten "the most colorful cave grottoes in the world."Photograph: Ansgar Koreng