Climb right into the heart of this colorful Iceland volcano.

Iceland's "Smoky Valley" is a beautiful river that is shrouded in a constant cover of steam clouds.

Walk in the footsteps of the gods and straddle two tectonic plates.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

Iceland's largest lagoon is home to stunning multi-colored icebergs.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

This fantastical waterfall is hidden in a cave located in a cracked cliff.

Rising from the sea like a stone monster.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

Medicinal spa created with the discharge from a geothermal energy plant.

This volcanic cave lake is essentially hard proof that Iceland is the most magical place on Earth.

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

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

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

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

The oldest arboretum on the Dalmatian coast doubles as the gardens of Kings Landing in "Game of Thrones."

Longest fortress system anywhere in Europe.

A wonderfully strange collection of 500+ stuffed frogs doing people things.

The remains of a sunken military ship wreck visible through clear water.

Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

An ethereal glowing blue ocean cave in Croatia.

This ancient burial mound is accessed by an impressive Greek-built archway.

A castle perched precariously over the Crimean Sea.