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.

This outdoor gallery of sculptures along the East River was once a landfill.

An iconic Soviet statue of working-class people.

With over 10,000 lights, this engineering marvel lights up the city after dark.

Fresh wooden posts have been added to ancient holes to recreate a primitive henge clock.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

A creepy sculpture of a decapitated head invites viewers to see St. Louis through its empty eyes.

These red and black houses were awarded to the firefighters who saved their city from an enormous blaze.

The ruins of the first Spanish settlement in Puerto Rico.

This nearly abandoned "company town" is a ghost of Puerto Rico's once-lucrative sugar industry.

The abandoned remains of this once-thriving hotel looms over the city, awaiting an uncertain future.

Legend tells how a Spanish soldier disappeared from this isolated sentry box without a trace.

This tiny home was originally a narrow alleyway.

This chapel on a cliff is renowned for its healing powers and was founded on the site of a supposed divine intervention.

This giant bronze image of Christopher Columbus embarked on a voyage of its own.

This bleach-white graveyard overlooking the ocean is accessed through a tunnel.

This limestone cave offers an incredible view of the Río Grande de Arecibo valley.

The smaller of the three towers of San Marino is a former prison inaccessible from the ground level.

An imperial church bombed to ruins during WWII now stands as a jagged memorial.

This home designed for chocolate magnate Antoni Amatller is an exquisite treasure-box of Catalan Modernism.

An underground network of massive stone arches and their skylit vaults support ruins of portico structures above.