Ringing Rocks County Park

Ringing Rocks County Park in Bucks County, Pennsylvania contains a seven-acre field of volcanic boulders that produce metallic bell-like tones when struck with a hammer. About 30% of the boulders ring. Geologists still debate why — the leading theory involves internal stress from the rock's formation — but no definitive answer exists. Visitors come armed with hammers to play the world's strangest percussion instrument.