A mud statue stands in the dark tunnels, seeming to hold up the weight of the city above.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

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

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.

Inside this McDonald's you can dine on your Big Mac and fries next to a 2,500-year-old Roman wall.

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

New Zealand's epic shrine to all things puzzling.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

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

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

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

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

Rome's first modern graffito is all that is left of a peaceful protest from the 1970s.

The martyr's wax-enhanced skeletal remains lie preserved in a glass case in the Santa Maria della Vittoria in Rome.

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

This elephant kraal is the only one remaining in Thailand, dating back to the 16th century when these massive mammals were integral players in war and trade.

This bridge made famous in a novel and on-screen wasn't actually built over the river Kwai.

A man's head is enshrined beneath a statue near the first building constructed for the modern Olympic Games.

An ancient octagonal weather station named for the eight Greek gods of wind.

This vast masterpiece of Moroccan architecture spreads across 20 acres.

The largest madrasa in Morocco once housed more than 900 students within its exquisite walls.

Deliberately hidden for centuries, the magnificent Saadian Tombs were eventually uncovered in 1917.