The gigantic skull of a long-extinct species that once roamed the forests of England and Ireland.

The Art Deco artwork depicts gilded carriers of deadly illnesses.

These mysterious Viking chess pieces spent centuries hidden on a remote Scottish island.

This marine reptile was discovered by one of the 19th century's greatest fossil hunters.

This open-air mosaic gallery honoring an English artist took hundreds of volunteers more than seven years to create.

The pretty iron lamp is a reminder of the architecture underneath London's streets.

The commemorative stone column conceals a secret laboratory.

An architectural oddity hides in plain sight on this iconic London bridge.

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.

The "lost friend” is the most famous of the six moai statues that were removed from Easter Island.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

The library houses an incredible collection of some of the world's most impressive books and manuscripts.

The fierce beast perches atop a pedestal marking where the historic City of London gates once stood.

A naturally mummified 2,000-year-old man.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

This coffee shop lies hidden beneath a historic church.

These 12th-century catacombs carved into a mountainside were a place of mysticism and Christian hermitages.

Ugly 18th-century dwarf statues living in a perfectly landscaped Austrian garden.

A prehistoric landscape hidden in the cliffs of Maha'ulepu.

This ruined fort and statue are a testament to the last king of Kaua‘i’s savvy diplomacy skills, which briefly brought Russians to Hawai‘i.

A burial ground for workers at one of Hawai'i's largest sugarcane producers that laid buried for decades.

The lobby of this hotel near the U.S.-Mexico border features a stained-glass mural that measures 42 feet long and 6 feet tall.

This church on a Tohono O'Odham reservation has stood since 1797.

This once-booming Gold Rush town is now home to a herd of feral donkeys.