Skyline Caverns, about 1 mile south of Front Royal, Virginia, is a geologic cave system estimated to be 50 to 60 million years old and opened to the public in 1939. Retired geologist and mineralogist Walter S. Amos discovered it on December 17, 1937, while searching scientifically for caves that could be developed with Skyline Drive. After investigating a dry sinkhole and signs of underground dampness, he uncovered a large connected system whose passages were mostly naturally navigable, though thick mud and clay had to be cleared. The caverns are especially known for protected anthodites, along with streams and other mineral formations seen on guided tours.

Photo: Wikipedia · Public domain

Photo: Wikipedia · Public domain

Front Royal, Virginia · USA