Building owners can take out tiles for free at this repository for historic building materials.

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

A sixth-century Byzantine cistern hidden below a modern carpet store.

A collection of modern and vintage pinball machines housed in the cellar of a 15th-century building.

St George's Leprosy Museum depicts the gruesome afflictions of those suffering from the disease.

This former medieval prison now unlocks Estonia’s rich photographic history.

"There's nothing there," and other lies the KGB told us.

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

This subterranean shrine beneath a bike rental store celebrates the iconic Italian scooter.

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.

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

According to legend, this tomb holds the secrets to time travel.

Perhaps the most spectacular grotto along the Algarve coastline.

This centuries-old Italian chapel hangs midway down a sheer cliffside.

The overgrown ruins of this once majestic castle sit forlornly in the Scottish countryside.

More than a century old, this cast iron bridge on the Balmoral Estate leads to nowhere.

This Scottish castle has witnessed clan rivalries, Jacobite uprisings, whisky smuggling, and more.

This giant boulder is pinched over a 1000-meter abyss by two mountains.

An underground city of salt.

A small window on Via Piella offers a lovely and rare peek at Bologna's lost canals.

A rare rune stone dedicated to a woman.

The second oldest anatomical theater is housed in a museum of curiosities.

The second-largest collection of runic calendar staffs in Sweden.