Water

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.

One of the few cold geysers in Europe, its eruptions are powered by carbon dioxide.

These cascading falls resonate throughout the Bulgarian forest.

This hydraulic power system in London was, at one time, seen as a rival to electricity and the last of its kind to shut down.

The widest natural waterfall in Estonia is a sight to see in all seasons.

As fallout from an irrigation project, a formerly cottonwood-lined stream is now a sandy, desolate, post-apocalyptic channel lined with weathered stumps and tumbleweeds.

The disdain for this dysfunctional dam is reflected in a giant pair of scissors painted on the concrete face.

An improbable waterfall springs from an orange-white cliff face, tumbling into the headwaters of the Virgin River above Zion National Park.

More than 25 fully functional scale replicas of famous lighthouses dot the shores of Lake Havasu.

In Lago Superiore, the largest expanse of lotus flowers outside of Asia is hard to miss.