Galápagos Lagoon As startling as a bright-blue eye, a central lagoon peers out from Rocas Baimbridgen in Ecuador's Galápagos Islands. The stark, rocky island teems with life at times—the brackish lagoon waters are favored by flamingos.

Riverbank Butterflies Leaf-green pierid alight on the sandy shores of the Tuichi River in Bolivia's Madidi National Park. The vast Madidi wilderness encompasses a staggering range of ecosystems—from snowcapped Andean peaks to tropical Amazonian lowlands.

Lounging Walrus A large, male Atlantic walrus rests with his tusks dug into the sand in Alaska's Togiak National Wildlife Refuge. Walrus tusks are multitaskers, used to grip the ice when hauling out of the water, wielded as weapons in territory or mating battles, and even brandished against attacking polar bears.

The Hard Way With bare hands and steel nerves, teammates pull down a wild horse at La Rapa das Bestas, or the Cropping of the Beasts, a festival held in Vimianzo, Galicia, in northwestern Spain. The tradition of wrestling horses to the ground in order to trim their manes and tails goes back, say Galicians, to Celts who settled the Iberian Peninsula by the seventh century B.C. Though the Romans eventually vanquished the Celts, their heritage has persisted in northwestern Spain, aided by later migrations from other parts of the Celtic realm. Someone from Ireland or Wales or Brittany who hikes the damp coastline dotted with circular ruins, stops in village taverns to hear bagpipe music, or finds a church with a holy well beside it, would swear that Galicia almost feels like home.

Mer de Glace Outfitted for a day of ice climbing, students test their skills on a glacier named the Mer de Glace, or Sea of Ice-one of the largest glaciers in the Alps. It extends eight miles (12 kilometers) on the northern side of Mont Blanc near Chamonix, France. Like other glaciers throughout the Alps, this one is receding. If current trends hold, scientists predict that 50 to 80 percent of remaining Alpine glaciers could vanish by 2100.

Uzon Caldera As summer's exuberance fades, sunset colors steal across tundra dimpled with ponds in Uzon Caldera. Tourists may visit this basin and the nearby Valley of Geysers on a few carefully planned paths—the only public access to the 2.8-million-acre reserve.