A truck tire 12 feet tall vies for attention at Utah's Kennecott Mine.

By Eric Smillie

The Colorado River spent 6 million years carving the Grand Canyon. It's taken Utahans only a century to dig Kennecott's Bingham Canyon Mine. At nearly three miles across and three-quarters of a mile deep, the open pit is the largest excavation on earth. "It's so enormous you lose perspective," says Dereck Bradley, who visited from San Diego with his family. "Your mind just doesn't comprehend how big it is."

In 1903, workers began digging for copper ore on a mountain 25 miles southwest of Salt Lake City. The pit is now the world's richest source of the key metal—think electric wire. Near the visitor center, guests pose by a tire from one of the mine's 80 trucks, each as big as a two-story house. The fleet travels 10,000 miles every 24 hours to haul out 450,000 tons of rock. Detonations shake the ground several times a day. "The kids loved that," Bradley says. (801) 204-2025, kennecott.com.