Kjeragbolten, Norway

Kjeragbolten is a boulder wedged in a crack in Kjerag mountain above Lysefjord in southwestern Norway, about an hour from Stavanger. The rock, about 180 cubic feet in size, hangs about 3,228 feet above the turquoise fjord, held in place by nothing but friction. Walkers set out from Øygardstøl near Lysebotn and the trail runs about 7 miles round trip, climbing about 1,870 feet over steep granite slabs with fixed chains, taking most hikers six to eight hours. The best time to go is June through September, when the snow has melted and the mountain road is open.