The great thing about our struggle to the top of Volcán Licancábur (19,652 feet or 5,962 meters) was the tri-border view of the Altiplano. From its flat, pebbled top, marked by the ruins of an Incan sacrificial hut, we looked out over the intersection of Chile, Argentina and Bolivia and the 4,000-kilometer (2,485-mile) circuit we had just completed—from Miscanti and Meniques in Chile, to Laguna de Vilama in the northwest corner of Argentina, to the long line of mineral-painted volcanoes that march south through Bolivia. Squinting, we could almost make out the coastline at Antofagasta, where our journey had begun.

Of course the physical beauty stands out, especially when you're standing on top of the tallest volcano around. But the people we'd met came rushing back, too. There was Celso, the salt miner who worked long hours with his wife, both masked against the glare of salt and sun; the Argentine rancher Señor Cruz, and his four generations of family living across from Río Rosario; the vegetable farmers in Talabre—a centuries-old oasis at the foot of Chile's Volcán Lascar—and their sophisticated irrigation system.

And though, from our mountain perch, we can see the enormous Laguna Verde and other small mountain lakes shimmering in the distance, it was our constant search for water that linked everything together. I recall the day that Zahel, standing in the middle of yet another Death Valley, surrounded by the bleached bones of cattle and burros, shouted down into a water test pipe, Agua! Agua! Agua!; the night our team slept beside a river of gold after struggling to paddle across Argentina's Laguna de Vilama, though it was only 3 centimeters (1.18 inches) deep; the Sunday afternoon I observed what seemed to be the entire population of the small, Bolivian town of Copacabana sitting around a shallow reservoir of fresh water, miraculously sprung-up in the heart of the desert; and then the final push on to Lago Polques and its thermally-heated pool, where, after nearly 7 weeks on the road, we were finally able to wash off our accumulated Altiplano road dirt. Even here, from the top of this tall mountain, smack in the middle of the driest place on earth, we can see how water is the one resource that ties the whole region together. And we are reminded, after a tiring search, that if you look hard enough, you can find what you need.

Agua! Agua! Agua!

Funding for this expedition was provided by the National Geographic Society Expeditions Council. For more information on the Council, its projects, and grants, e-mail ecouncil@ngs.org.