The Atta Cave or Attendorn Dripstone Cave in Attendorn is one of the largest dripstone caves in Germany. The cave was discovered during the quarrying of limestone at the Bigge Valley Limestone Works on 19 July 1907 and was opened up by the owners to tourists that same year. Today the Atta Cave is the most-visited show cave in Germany, receiving around 350,000 tourists per year, and is an important economic factor for the town.