Two stone columns flank the grand Venice square, but there were supposed to be three.

Go inside to really appreciate this 500-year-old technological masterpiece.

Where Venice's gondolas go for a tune-up.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

The Italian revolutionary's legendary wife is portrayed on horseback waving a gun and holding her child in this memorial on the Janiculum.

This is the oldest Roman-made bridge in the city still existing in its original state.

This statue is the only female representation of Rome's "talking statues."

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

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

This saltwater swimming pool, which is the last of its kind in the United States, is slowly crumbling within sight of multiple high-end beachside hotels.

A sculpture of the famous photograph stands on San Diego's "Greatest Generation Walk."

This oversized flute-playing Ancestral Puebloan deity is also a landmark of Southwestern kitsch.

A small park on Bourbon Street features life-size bronze statues of New Orleans musicians.

The South's nickname was supposedly born at a former bank in New Orleans' French Quarter.

The unluckiest U-boat in the entire German fleet is now on display in a Chicago museum.

A beloved Chicago music venue offering cold beer and lots of “Friendly."

Beloved bar home to musicians of all eras and reputations.

The palatial McDonald's that inspired Wesley Willis.

In 2004, a Dave Matthews Band tour bus dumped 800 pounds of waste off a bridge and onto an unsuspecting tour boat below.

The twin towers in this Chicago fountain use 50 foot tall video screens to spit on people.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

Where commuters walk through remnants of an ancient Greek necropolis.