More than 5,000 years old, D27 is the largest dolmen in the Netherlands and was already standing long before Stonehenge and the Egyptian pyramids were built.

Incredible labyrinth of man made caves.

The world’s first interactive human body museum also serves as a chair for a giant orange man.

The world's longest wildlife overpass provides Hilversum's critters with a safe alternative to trying their luck on the roadway.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

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

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

Europe's official "zero-level," the equator of elevation.

Spain's largest bullring offers a unique glimpse at architecture and history.

The world's largest wooden structure.

Hidden behind a wall, Spanish nuns distribute their signature sweets on a revolving tray.

An underground city of salt.

This large copper bolt represents the benchmark for measuring sea levels in most of Europe.

A scenic UNESCO site that doubles as a habitat for various forms of wildlife.

A naturally beautiful, seemingly bottomless deep blue spring.

This ominous Albanian fortress houses tanks and downed planes as a reminder of their victories over Western imperialism.

Once the fallout shelter of a dictator, this sprawling bunker is now a combined history museum and contemporary art gallery.

In this town's main square resides a statue of none other than the 43rd President of the United States.

The elliptical citadel resisted the advance of the mighty Ottomans several times, thanks to the military prowess of the "Dragon of Albania."

According to a local legend, this old castle could only be built after a woman was immured in the walls.

Once a safe haven for locals engaged in blood feuds, this 400-year-old fortified tower is now a museum showing what life was like for those lying in wait within its walls.

An Albanian monument to the Communism that nearly crushed the country is now a crumbling wreck.

Beneath Kraków Old Town's main square lies a hologram-filled medieval market vampire graveyard wonderland.

An eerie, existential museum dedicated to the author of "The Metamorphosis."