During World War II, this rice mill became a Nazi concentration camp.

The most confusing clock in New York.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

This former Roman Catholic Church still contains the embalmed hearts and organs of 22 popes.

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

2300-year-old Roman road connecting the empire.

Budapest's Communist-era statues, banished to the suburbs.

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

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

Mountain where Jesus was first tempted by the Devil.

A popular shrine where the Blessed Virgin allegedly appeared in 1830, displaying a holy armchair and two incorruptible remains of Lady Saints.

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

This bridge was constructed from the rubble of the infamous Bastille.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

This one-room museum is dedicated to Norwegian history and jokes.

The world's northernmost aquarium looks like it has fallen over.