Legend says if this neo-Gothic basilica is ever officially completed, the world will come to an end.

These ancient ritual mounds are our best window into the culture of the ancient Mississippians.

A preserved portion of an ancient Athens barrier is displayed in a hotel basement.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

The oldest cemetery of modern-day Athens blends the modern and ancient worlds.

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

Little Red Lighthouse under the George Washington Bridge.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

Before it was buried by volcanic ash, this fast-food restaurant fed the hungry hordes of ancient Rome.

The oldest continuously-operating Chinese restaurant in the United States has been in business since 1911.

A much-loved sculpture depicting the hero of a 1956 anti-Soviet uprising.

A diminutive statue that was inspired by the sculptor's own daughter.

The only subway station in the city that still makes use of gap fillers.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

Northern Ireland's Brobdingnagian stepping stones.

Touching mementoes from those who didn't make it back from World War I still hang in one of New York's oldest bars.

This large, circular tomb is the final resting place of the first emperor of Rome.

A contemporary art installation housed within a Gothic cathedral.

Largest Roman Catholic church in North America.

A precariously balanced rock perches on the edge of a cliff created tens of thousands of years ago by glacial erosion.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

A small cell adjacent to this church was once the bedroom for a renowned saint.

The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

The remnants of a wooden-hulled fleet built and abandoned in WWI, now home to a thriving ecosystem.