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

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

This scale model of our solar system hid in plain sight for years before a physics team sought out all the planets.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

A musical instrument played by the sea.

An ethereal glowing blue ocean cave in Croatia.

An abandoned saucer-shaped monument in the Bulgarian mountains.

This historic black and white monastery is one of Bulgaria's architectural jewels.

This ancient theater, restored in the 20th century, lives on as a venue for dramatic and musical performances.

A vast Communist-era exhibition space in the Bulgarian capital.

This brutalist monument is inscribed with 9921 names of Yugoslav partisans who perished during WWII.

There's a mini version of Iguazu Falls hidden in the Balkans, and it's got a rope swing.

Bridge that died in war and was resurected.

This collection of solar timekeepers includes the world's first digital sundial.

An undulating wicker beast looms peacefully atop a sand dune in Belgium.

A maze of crosses marks the jumbled divide between the Netherlands and Belgium.

A 14th-century fortified keep showcases the masterpieces of an ingenious 20th-century clockmaker.

Part modern art project, part traditional chapel, this see-through church is only substantial from the right angle.

Lavish royal estate punctuated with heated greenhouses.

A magical and peaceful ruined Cistercian abbey in what is now southern Belgium.

Hiding the longest subterranean river known in the world.

Climb inside an iron crystal magnified 165 billion times its normal size.

Each spring, a dreamlike carpet of bluebells overtakes the forest floor.

Resting in the middle of an Austrian river, this sci-fi "island" lets people cross in neon style.