Inside this building is another country within Rome, a sovereign entity without a physical territory.

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

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

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

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

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

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

Museum dedicated to literary greats of the Romantic Period is also the home in which Keats met his untimely end.

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

The London pub overlooks where the Mayflower was moored before setting sail for the New World.

Everyone from Alan Ginsberg to The Rolling Stones has stopped by this classic dive bar.

Once the site of a Native American harvest festival, this humble clearing later played an invaluable role in the birth of jazz.

This distinctive Crescent City tradition dates back to the days of horse-drawn carriages.

A 200-year-old building in the French Quarter that was to be Napoleon's home in the New World.

The oldest family-run restaurant in the United States is a living museum of New Orleans dining history.

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

A 200-year-old bar in the historic French Quarter refuses to give up its place in history, nor its role in securing ours.

The only rotating bar in New Orleans has been slowly spinning since 1949.

This bar named after the world's first mixed cocktail was home to one of New Orleans' most notorious politicians.

A snapshot of the city's fascinating voodoo culture.

Where condemned pirates met their grisly end at the gallows on the River Thames.

A discarded movie prop that was the original monolith for "2001: A Space Odyssey."

Never actually a tree at all, this spot was the site of London's public hangings for nearly 600 years.

Graffiti from the 16th and 17th centuries cover the walls of this part of the Tower of London.