The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

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

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

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

Architectureal fantasy quarter of Rome.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

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

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

This island castle contains enough secret passageways to support a season of Scooby-Doo episodes.

This 29-ton granite ball spins around at the slightest touch thanks to a scientific phenomenon.

What was meant to be a temporary exhibit is now a permanent fixture at the St. Louis Zoo filled with beautiful birds.

The "World's Largest Underground Business Complex," a 55,000,000-square-foot city underneath Missouri.

Curious cave that stays a cool 56 degrees all year long.

The world's oldest rose is so tough it survived being bombed in World War II.

A 32-acre fun park dedicated to all things cheese.

A measuring mishap led to these artificial stone ladies losing their stomachs.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.

A library where thousands of books explain how to avoid another Great Recession.

Floating man-made island and upscale restaurant.

The second oldest continuously operating bar in Louisiana.

Last stop before the top of the highest peak in the world.

A pub that is literally in the middle of nowhere, but continues to do business.

The world's most remote permanent settlement on an active volcano.

The cafe that acts as the social hub for the small volcanic island of HMS Bounty fame.