This medieval city gate is now a blend of the past and the modern world.

Every day is like Christmas on this street where the traditional Neapolitan nativity scene comes to life.

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

The world's largest piece of copyrighted artwork.

This landmark cemetery in Boston was created more than 300 years ago.

The site of Paul Revere's historic two lantern warning.

In 1958, an MIT fraternity pledge laid down on this bridge and instituted a new, unique unit of measurement.

One of the indelible moments of the American Revolution took place at this location.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

Ancient snack bar of the Roman Empire re-opened.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

The walls and streets of the ancient city are peppered with penises.

Erotic art covers the walls of the largest ancient pleasure palace.

At the time of its completion, it was the tallest dam in the world.

Hidden in the Santa Ynez Mountains off Highway 154, this tiny restaurant once served as a stagecoach stop.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

A beautiful geyser under environmental threat.

Elvis's own personal tropical hideaway.

The hotel where Martin Luther King Jr. was shot is now a museum dedicated to his work.

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

The longest continuous lava tube in Oregon.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

This immigrant bridge once spanned the Thames but is now a fixture of an Arizona city.