Leveled by an earthquake, this Italian village is now preserved as a massive concrete art project.

This amazingly preserved Doric temple was abandoned before it was ever completed.

Behind medieval walls in a corner of bustling Palermo is a breathtaking former mosque once inhabited by a wolf-taming hermit.

The former atelier of Mario Cassisa is a treasure trove of paintings, sculptures, and artist books.

A collection of grotesques lines the walls of this Italian villa.

Haunting graffiti left by prisoners of the Spanish Inquisition.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

An off-the-beaten-path boutique stuffed with an eclectic collection of upcycled goods.

This banal Parisian entranceway is not what it seems.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

Hundreds of secret cabinets built into the walls of legendary poisoner's private work room.

An unusual round church in London with a Templar past.

A vast overgrown cemetery, once known as one of London's "Magnificent Seven."

The curios of pharmacist and collector Henry Wellcome.

The last four extravagant street signs of London's historic banking street.

This South London cemetery holds the remains of more than 15,000 people.

This macabre painting of a Shakespearean scene looks like something out of a nightmare.

This mysterious and unique painting is filled with symbolism.

Tucked away behind the mansions of Mayfair, this picturesque garden is a hidden London treasure with a spooky past.

The television series' iconic giant foot was borrowed from this classical painting.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

This long-hidden space above Westminster Abbey now displays the battle gear of the legendary King Henry V.

The "beautiful" equation predicting the movement of all electromagnetic particles is engraved in front of Newton's tomb.