Stockholm's deepest subway station is also a stunning ecological wonder.

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

An illuminated manuscript comprising the life's work of a lone monk, inexplicably decorated with a portrait of Satan himself.

This medieval castle was painted pink as part of a now-abandoned children's theme park.

A monument hidden in the woods built in 1938 as a getaway for a Dutch museum curator.

The ruins of a medieval castle that once belonged to one of the most powerful families in the Netherlands.

This neighborhood of futuristic ball houses looks like an alien settlement in a science fiction film.

Drive past the giant fruit sculptures and up to the window for a menu of fruity treats.

Visit the ancient, mysterious Roman catacombs ... in the Netherlands.

The giant scales in this museum can still tell if someone is one of the devil's brides just by weight.

Crouch down, stretch tall, and be sure to flail your legs to pay homage to the Monty Python classic.

A true Valhalla for cactus and succulent lovers.

The ruins of this Dutch castle sit atop a labyrinth of once-secret tunnels and passageways, dating back over 900 years.

A poignant museum dedicated to the history of the Dutch resistance against Nazi occupation

This massive mural by famed pop-artist Keith Haring was hidden for almost 30 years until its 2018 rediscovery.

The Bloemen Route, or “Flower Route”, stretches 25 miles through prime Dutch tulip country as a result of “tulip mania,” the world’s first economic bubble.

This museum housed in a former brothel explores the past and present of sex work in Amsterdam.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

This cheese shop also houses a museum devoted to Dutch dairy.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

On the edge of the Valles Caldera National Preserve, these rock formations create an eerie landscape.

The hallowed remains of a 900-year old Ancestral Pueblo great house.

Its history includes dinosaur fossils, cattle rustlers, Georgia O'Keeffe, and a mythical giant rattlesnake named Vivaron.