Mercer Caverns is a show cave located one mile north of Murphys in Calaveras County California. It is named after the gold prospector Walter J. Mercer who discovered the caves around 1885 and filed a claim. The caverns have a large number of speleothems, stalactites, and stalagmites. It is formed in a marble unit known as the Calaveras Formation. It also contains a large display of aragonite frostwork.