Even at 100, Grand Canyon National Park is as astonishing as ever. Walk to its edge, and the earth falls away into an expanse of peaks, plateaus, and gorges so vast it can be disorienting. Descend below the rim, and the sense of awe only grows. The canyon is essentially an inverted, 6,000-foot, 277-mile-long mountain range, where you are dwarfed by sheer stone walls stacked to the sky and vistas that multiply with every turn. In the desert landscape, the water can be the most astonishing sight. Turquoise streams rush whole out of rust red cliffs and cascade through travertine pools. At the bottom of the canyon, of course, lies the engine of this great geological conundrum—the thrumming, persistent Colorado River, which carved the gorge over millennia. If there’s a better place to gain perspective on our own relative insignificance, I don’t know it.