Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

The world's longest known cave system.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

A beautiful geyser under environmental threat.

Construction of Barcelona’s iconic (but controversial) church was finally completed in 2026—a century after the death of its architect.

Crypt mausoleum in cathedral's basement contains relics of third century Roman martyr, Saint Vibiana.

The first declared National Monument in the United States.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

Towering basalt columns, a creation of fire and ice.

The site of the climactic scene from the classic horror film is now a historic landmark.

Macabre astrological automaton clock dating to the late 1400s.

Elevated freight railway turned wildly successful urban park.

A church of bones, decorated with 40,000 human skeletons.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

A sharp bend in a dramatic river canyon cut through red rocks.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Most-visited and most-photographed slot canyon in the American Southwest.

The world’s first penitentiary, meant to be humane, drove men insane.

Rippling sand dunes frozen in the Arizona rock.