Set on a mountainside otherwise composed of reddish gravel and dark volcanic rocks, this prominent outcropping of white limestone and marble dominates the Sherwins Meadow and Hidden Lake like the ruins of some medieval fortress. It was just this sort of radical geological feature that infected 19th-century prospectors with dreams of fabulous ledges of high-assay gold, and to this day you'll find evidence of early mining activity: old timbers and rusted cable and even the entrance to a deep passage dug into the core of the rock itself. Easiest access to the rock is from the trailhead on upper Old Mammoth Road.