One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

Secret Swing.

A collection of more than 12,000 shoes, displayed in a building shaped like a shoebox.

Eastern Canada's ocean playground.

The final resting place for the remains of 143 Habsburg royalty.

Once called the "Polish Gold Coast" it is an icon of the neighborhood that bears its same name.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

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

This exemplar of modernist architecture is meant to captivate and inspire students of the Cooper Union.

Dodge prohibitionists and slide through the telephone booth in Crif Dogs.

Make a tough dinner decision: Octopus wasabi roulette or bull penis?

Paris' fabled purveyor of exotic taxidermy and natural history curios.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

After a profound show of devotion for his master, a dog becomes the symbol of loyalty for an entire nation.

Skulls from the plague of 1656 and World War II bombings are united by a cult dedicated to caring for the ancient dead.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

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

A Nesting Doll of Churches.

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

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

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

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