Mysterious rocks that ring musically when struck.

Reclaimed by nature, the ruins of Doodletown, New York are remnants of a town consumed by a state park.

This evocative New Jersey statue memoralizes the Polish victims of a Soviet massacre.

This stone tower marks a lookout point over the historic Washington Crossing, and maybe some buried treasure.

New Jersey's last historic covered bridge was rebuilt from pieces of the original 19th-century structure.

A sculpture serving as an homage to Pope John Paul II.

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

2300-year-old Roman road connecting the empire.

Plaques on its facade commemorate the Tiber's most destructive deluges.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

This one-of-a-kind Roman arch is not actually dedicated to the god Janus.

The only remaining arch of the oldest stone bridge in Rome stands in the middle of the Tiber.

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

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

The studio built by fascists in the hopes of "reviving the film industry" with the occasional propaganda film opportunity thrown in.

This curious, round temple is the oldest still-standing marble building in Rome.

The "Great Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

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

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

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