Water

It takes a nine-mile hike to reach these hot springs, but weary hikers are rewarded with stunning views and a warm soak.

A waterway covered over after the Industrial Revolution has been unearthed and cleaned up, for the enjoyment of fish and humans alike.

This environmental engineering marvel keeps salt water from the Elizabeth River.

A well drilled into the side of a cliff supplies most of the water consumed on the island of El Hierro.

Hidden in the New Mexico desert southeast of Roswell, nine small deep lakes formed inside sinkholes.

Long buried under the 20th-century landscape, this lift lock of the Alexandria Canal is the lone remnant of an ambitious early American transportation project.

Nearly 800 years old, this river lock is now a public park with a former fortified island.

A network of underground water channels that dates back to the Middle Ages.

Cascading waterfalls mark the gateway to the ancient burial place of Clan Macnab.

One of Indonesia's tallest, this waterfall takes a 390-foot plunge into the Lake Toba caldera.

Nine caves filled with recently-discovered archaeological finds under the houses and the streets of the most ancient district of an old town.

In one of the hottest parts of the Mojave Desert, shallow bedrock forces the typically dry Mojave River to the surface in this canyon, providing a vital oasis for humans and wildlife.