Just off Highway 4, about a mile north of Murphys off Sheep Ranch Road, are the Mercer Caverns. These caverns, discovered in 1885 by Walter Mercer, contain a variety of geological formations -- stalactites and stalagmites -- in a series of chambers. Tours of the well-lit caverns take nearly an hour. From Memorial Day through September, hours are Sunday through Thursday from 9am to 5pm, Friday and Saturday from 9am to 6pm; from October 1 to Memorial Day, hours are 10am to 4:30pm daily. Admission is $12 for adults, $7 for children ages 5 to 12, and free for children under 5.