The curious underground history of keeping Paris clean.

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

This large, circular tomb is the final resting place of the first emperor of Rome.

Mummies preserved naturally for seven centuries.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

The site of London's first coffee house has been serving refreshments of one kind or another for 360 years.

Rebuilt remains of a temple to Roman god Mithras.

The curios of pharmacist and collector Henry Wellcome.

A kaleidoscopic warehouse-maze of handmade neon signs.

The largest known Ancient Egyptian obelisk.

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

The oldest stone house in Paris was built by its most famous alchemist.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

The floor-to-ceiling collection in an old factory is a unique alternative to stuffy galleries.

A bronze ballot box stands at the spot where Susan B. Anthony voted illegally.

Thirty creepy ghosts now inhabit this decaying 14th-century church.