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

This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

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

This ancient market is often referred to as the oldest shopping mall in the world.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

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

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

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

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

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

Rare recess caves fill this unbelievably beautiful Ohio park.

What's left of the ruins of the 1893 Columbian Exhibition, or World's Fair, also known as the White City.

Every day a troupe of pampered water fowl walk the red carpet to their favorite fountain.

The unbelievably opulent home built for an infamous newspaperman.

This replica of the Greek structure is in the heart of Nashville.

By day this New Orleans square is for pedestrians, but by night it is a kingdom of kittens.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

Though strikingly beautiful, Seattle's other railway station is now largely forgotten.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

A castle built by an eccentric medieval enthusiast in suburban Ohio.

An abandoned relic of the city's failed experiment with below ground transit.