Mercer Caverns, Show cave in Murphys, California, US

Mercer Caverns is a show cave near Murphys, California, featuring an underground network of natural limestone chambers with stalactites, stalagmites, and flowstone formations throughout. The formations span roughly 1 kilometer through multiple levels and passages within the rock.

Gold prospector Walter J. Mercer discovered the cave system in 1885 while seeking precious metal. Instead of riches, he found human remains that scientists later studied, revealing the archaeological significance of the location.

The cave gained recognition at the Paris World Fair for its rare aragonite frostwork formations that visitors can see throughout the chambers. These delicate crystal structures grow on the rock surfaces and give the place a distinctive character among other caves in the area.

The cave can only be visited on guided tours that descend about 160 feet (50 meters) via several hundred steps and return upward through natural and artificial passages. The climb back up is more strenuous than the way down, so reasonable fitness helps.

The cave houses mineral displays of flos ferri, an unusual crystal formation rarely seen among the three publicly accessible caves in Calaveras County. This delicate mineral sets the place apart from similar natural sites in the region.