This rare volcano spews the strangest and (literally) coolest lava in the world.

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

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

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

The remains of this 2nd-century Roman temple are incorporated into a modern building.

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

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

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

A forgotten "city of water" underneath the famous Trevi district.

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

An ancient Egyptian obelisk is now used to commemorate fallen Italian soldiers.

A giant concrete egg marks this Indiana town as the "Egg Basket of the Midwest."

This burger joint is named after everyone's favorite carnival prize and is adorned with a giant one over the door.