Buried for centuries, this hidden cellar is all that remains of London's medieval Whitefriars Monastery.

This majestic tree has survived 400 years of storms, droughts, and floods, and is a beloved natural landmark in Missouri.

Although rarely used, there is still a hidden room for the royal family at the Stockholm central station.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

Islanders once used this dramatic, otherworldly landscape to hide their cattle from Viking raiders.

A secret fresh water spring for animals and humans alike hidden along the most famous road in the United States.

Everything you always wanted to know about borates is here.

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

A creepy sculpture of a decapitated head invites viewers to see St. Louis through its empty eyes.

This great stone guardian of the forest is a relic from the land's volatile volcanic past.

Its dark depths conceal millions of rare, delicate crystal formations.

Huts like this were once a hub for the female divers who collected pearls and seafood off Japan's coasts.

Potato-peeling mannequins, Inca art, and a dangling tuber mobile help trace the history of fries at this Belgian museum.

This triumphal arch celebrating the Sun King's conquest of Lille is a masterpiece of military architecture.

The first high-tech company in the valley that actually worked with silicon devices.

One of the largest free-standing structures ever built, this dirigible hangar is now simply a giant skeleton.

The burial place of 14 of the executed leaders of the Easter Rising.

This enormous World War II relic is one of the largest wooden structures in the world.

A moody and picturesque riverside ruin overgrown with vegetation.

This enormous censer uses a pulley system installed over 400 years ago.

Surrounded by ash fields in Iceland, an impossibly verdant valley looks like something out of a fairytale.

This amazing trail among the many waterfalls around Ingleton has been enchanting visitors since 1885.

Cycle the solar system—from the sun to Pluto—right here on earth.

A section of the long chain that blocked enemy ships from entering Constantinople.