Black cat statues guard this temple-like Egyptian revival factory.

The remains of a historic football stadium that once hosted 50,000 spectators.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

The construction of a tram line unveiled hidden remnants of the old medieval city.

A medieval military street hidden beneath a charming French fishing village.

Harlequin costumes, signed scripts, and armor-wearing puppets.

Ever hear of the Milazzo Cage?

The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

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

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

One of seven Jewish catacombs in Rome and one of only two open to the public.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

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

The final resting place of the poets Shelley and Keats.

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

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

The yawning maw of this pagan visage is said to bite off the hands of liars.

Inside a former cabaret, seven floors of erotic art.

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

An immersive projection art installation uses sound, scale, and light to take visitors inside classic works of art.

135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

Two awe-inspiring globes from the reign of the Sun King hang from the ceiling of France's national library.

A subterranean shelter remains intact under a busy Paris railway station.