Blue John Cavern

Up the southeastern side of Mam Tor, 2 miles west of Castleton, Blue John is a maze of natural caverns with rich seams of Blue John Stone that are still mined every winter. Access is via a one-hour guided tour that departs every 20 minutes, and involves a climb of 245 steps. A walking trail leads here from Winnats Pass, just west of Castleton; the tourist office has maps.