The Mist Trail follows the Merced River as it drops from the High Sierra to the floor of Yosemite Valley, a descent that geologists call the Giant Staircase. The river carved this path through granite over millions of years, but the staircase shape owes its drama to glaciation - ice sheets gouged the valley into a U-shape and left the tributary streams hanging at different elevations. The result is a series of shelves, and the Merced tumbles from one to the next. The trail begins at Happy Isles, where the river braids through boulder fields at the valley floor, and climbs 1,900 feet over 2.7 miles to the top of Nevada Fall. Along the way, house-sized boulders sit in the streambed like dropped toys, dwarfed by walls of exfoliating granite that rise 3,000 feet on either side. The scale tricks the eye. What looks like a short scramble to the next ledge becomes a thirty-minute climb. What looks like a modest cascade turns out to be Vernal Fall, a wall of water taller than a twenty-story building.

Between the two waterfalls sits a granite shelf where the Merced pauses and spreads into the Emerald Pool, named for the deep green color the water takes on as it slows over polished rock. Hikers who have just climbed through the spray of Vernal Fall sprawl on the warm granite to dry off, and the contrast is striking - the violent, roaring cascade below gives way to this eerily calm stretch of river, shallow enough in late summer to wade across. The shelf is a geological intermission, a flat pause in the river's otherwise relentless descent. But the calm is temporary. A few hundred yards upstream, the river gathers speed again, tipping over the lip of Nevada Fall in a 594-foot plunge that dwarfs the falls below. From the Emerald Pool, you can hear Nevada Fall before you see it - a low, constant thunder that grows as you climb.

The crux of the Mist Trail is a steep section beside Vernal Fall where the spray is so heavy that the granite steps become a waterfall in their own right. In peak spring runoff, visibility drops to a few feet and the roar of the water drowns out conversation. Hikers grip a single guardrail bolted to the cliff face and climb blind through the mist, their shoes squelching on stone. This is also the section where circular rainbows appear - the spray creates a curtain of water droplets between the hiker and the sun, and because the cliff behind acts as a dark backdrop, the full ring of refracted light becomes visible. Most rainbows appear as arcs because the ground blocks the lower half, but here the hiker stands on a narrow ledge with open air below, and the complete circle shimmers in the mist like a target. The effect is best in late morning, when the sun angle is steep enough to light the spray from above.

The Mist Trail connects to nearly every major route in Yosemite's backcountry. It is the most popular first leg of the hike to Half Dome, where climbers use steel cables bolted to the granite to haul themselves up the final 400 vertical feet. It links to the John Muir Trail, which shares the same trailhead at Happy Isles and winds 211 miles south to the summit of Mount Whitney. And from the top of Nevada Fall, hikers can continue into Little Yosemite Valley, where the river flattens out and the crowds thin. For those who prefer to look rather than climb, Glacier Point offers a bird's-eye view of the entire Mist Trail from 3,000 feet above. From that vantage, the Giant Staircase reveals itself clearly - Vernal Fall and Nevada Fall stacked like steps, the Emerald Pool a green comma between them, and the thread of the trail switchbacking up the cliff face, tiny figures moving through curtains of spray.