A miniature train-ride through Slovenia's largest cave system.

This massive subterranean fissure is known as the "underground Grand Canyon."

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

A crumbling World War I fort that is reached through a series of concrete tunnels.

The "dragon babies" of southeastern Europe.

This one-time health resort was used by aristocrats around the world.

Elaborate tile work in this railway station tells the story of Portugal.

This museum is home to one of the biggest collections of printing press technology—plus a river view.

A small but charming botanical garden that contains many exotic plant species.

This irregularly shaped sea fortress has defended not one but three different sovereign states.

An abstract monument to a symphonic composer.

One Portuguese poet described this cape, the westernmost point in mainland Europe, as "where the land ends and the sea begins."

This once-forgotten oasis in the middle of Lisbon was first created over a century ago quite by accident.

This tile-work piece featuring a chicken riding in carriage is both a remarkable artistic creation and a social commentary of politics and culture in 17th-century Portugal.

People from around the world visit the shrine of Japan’s legendarily loyal dog.

The verdant mossy ruins of a Franciscan monastery lie in the remote Sintra hills awaiting exploration.

In Portugal, a secluded stretch of untouched natural beauty hides at the bottom of a steep hill.

The grand, column-fronted, sculpture-adorned home of the ambitious digital library.

One of the few places in Portugal where the Celtic ritual of wearing large wooden masks is still practiced.

A windswept necropolis carved into the rocks overlooks the "most Portuguese town in Portugal."

This gaping hole in the middle of a remote mountain lake looks like a portal to another dimension.

A Japanese shrine to dolls.

Houses are tucked between, on, and underneath giant boulders.

This volcanic island in the Pacific just keeps growing and growing.