A fantastical 13th-century fortification sandwiched by a modern hotel in central Brussels.

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

A marble Lucifer hides behind the pulpit of this Gothic cathedral.

This abandoned Belgian fortress is purposefully being left to nature.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

This former Masonic lodge has been transformed into part museum, part bar, all awesome.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

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

This ghost town in Belgium will lose its street art when it ceases to exist.

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.

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

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

The colorful stairs are made with marble from the world's major quarries.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

A treasure trove of fine art is hiding inside this small medieval abbey in Gascony.

An architectural oddity hides in plain sight on this iconic London bridge.

Incredible rock formations jut from the southern end of this spectacular stingray-viewing spot.

This former Masonic hall has been turned into an art project that uses even more metaphysical iconography.

The little-known second castle that William the Conqueror built in York.

The medieval castle built as headquarters for the Pope's secretive Knights Templar.

Giant busts of 42 U.S. presidents are sitting in a field in Virginia.

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

You can spend the night in Dr. Frank-N-Furter's castle.