Coral Caverns & Show cave is the only fossilized coral reef cavern known to be in existence. The famed caverns has amazed thousands for over 80 plus years with the diversity and beauty of its natural cave formations. One of the most distinctive features is the coral reef, a towering fossil wall, containing the fossil remains of coral and other sea-creatures buried over 400 million years ago when Pennsylvania was partially covered by ''The Great Inland Sea.''