Hibiscus Petals.

Bright petals mark the hibiscus, a flowering plant found in much of the world.

Giant Lobelia
The leaves of a giant lobelia plant, photographed on Mount Kilimanjaro's Shira Plateau in Tanzania, spiral around the center.

Antelope Canyon, Arizona

Sunlight sneaks through a crevice in Antelope Canyon near Page, Arizona.

Quaking Aspen Trees

Quaking aspen trees in California's Sierra Nevada Mountains are resplendent in shimmering foliage and white bark.

Knotted Aspen Bark

Knots peer out from the bark of these North American aspen trees.

Turbines at the Barrage de la Rance electric power generating station in France create a whirlpool in the Rance River.

The Colorado River circles through Horseshoe Bend near Page, Arizona. The Colorado flows 1,470 miles (2.366 kilometers) from the Rocky Mountains to the Gulf of California's Sea of Cortez—or did when its waters were more plentiful. Reduced rainfall and the growing water demands of some 30 million thirsty Westerners have sucked some of the life from the Colorado, and these days its delta is often dry.

Iguazú Falls straddles the border between Argentina and Brazil just downstream from Paraguay. Over 5,000 cubic meters (176,573 cubic feet) of water plunge down 275 cataracts every second.