This 47-story "M" needed 20 years to be completed

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

Commonly acknowledged as the only public monument to the Devil himself.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

An ancient Egyptian temple in the middle of Madrid, Spain.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

France's most famous cemetery, with some of its most curious tombs.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

Beneath the impressive baroque cathedral that rises from the center of Berlin lies the largest collection of Prussian royals in the world.

The most visited, and possibly most controversial, museum in Germany.