Monasteries on rock pillars, once accessible only by frayed ropes.

This historic structure has been used as a mosque, a barracks, a prison, a school, and a bakery.

Where commuters walk through remnants of an ancient Greek necropolis.

A sharp sculpture made of thousands of pieces of jagged glass.

An ancient octagonal weather station named for the eight Greek gods of wind.

The railway carts travelers to central Athens's highest peak, which offers stunning vistas of the city.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

This charming wooden church was disassembled and moved not once but twice before settling in this Prague garden.

Wall Street has a new heroine, a bronze statue of a small but fierce girl.

A beautiful collection of architectural ornaments rescued from demolished New York City buildings.

A controversial magical figure is hidden within a diorama of the city.

The largest Roman amphitheater in the Balkans once held over 20,000 people, but managed to lay hidden for hundreds of years.

This Roman monument is surrounded by more recent construction, offering a stark contrast between ancient architecture and the modern urban landscape.

Home to what was once considered the largest gate in central Asia.

This miniature village stays behind in the Breuer Building, even as the museums around it come and go.

This lesser-known Frank Gehry building houses a treasure trove of cinema history.

Fake subway tiles were installed to cover a design that resembled the Confederate flag—it's unclear if the resemblance was intentional.

This picturesque monastery at the base of a cliff is a peaceful oasis open to all visitors.

Berkeley Springs State Park boasts the nation's only monument commemorating presidential bathing.

A sharply wedged sundial marks the point at which each day in the United States begins.

Rumored to be the famed pirate's lookout tower, this historic stone structure is now just watching for tourists.

This stucco building in North Africa was the first American-owned property on foreign soil.

If it hadn't been caught in time, a flaw in the design of this Manhattan skyscraper could have led to its collapse.

Backwards hour and minute hands and a timing mechanism that fluctuates with the temperature led to this clock tower's local nickname.