A great before-breakfast or pre-sundown hike at Grand Canyon National Park's North Rim is the short walk to Bright Angel Point.

While the glaciers interspersed along the peaks of Glacier National Park weren’t responsible for the enormous U-shaped valleys, their gradual disappearance brings a sort of urgency to see these classic icons.

The Appalachian National Scenic Trail is arguably the world’s most iconic long-distance trail. It falls and rises, swaggers and turns, following meanders for 2,185 miles from Mount Katahdin in Maine to Springer Mountain in Georgia.

We splash downstream in The Narrows of the North Fork of the Virgin River, deep in the backcountry of Utah’s Zion National Park, mostly craning our necks up like turkeys hypnotized by falling rain. But our fascination is not with rain, but red walls on both sides that rise hundreds of feet overhead. The sun does not find us in this deep canyon, where the air temperature approximates the inside of a refrigerator, and the ankle- to calf-deep water feels about the same.