The Hidden River Cave, which is now operated by the American Cave Conservation Association, was once the source of drinking water and hydroelectricity for the city of Horse Cave, Kentucky. Groundwater pollution from domestic and industrial sewage closed the cave in 1943. For the next half century it was used as an open sewer. In 1987 Hidden River Cave was restored, and a museum and educational center were established. The cave, which has been called "the greatest cave restoration success story in the United States" is now open year-round to visitors.