Speedwell Cavern
The area's most exciting cavern has 106 slippery steps leading down to tunnels blasted out by 19th-century lead miners. You transfer to a small boat for the claustrophobic ¼-mile trip through an illuminated access tunnel to the cavern itself. At this point you're 600 feet underground, with views down into the so-called Bottomless Pit, which is filled with water. An on-site shop sells items made of Blue John, a mineral found nowhere else in the world.
