This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

Once the home of a hermetic monk, this cave now houses a small church.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

Wonderland replication in progress by one persistent man.

A unique seaside cave where Aleister Crowley faked his own death.

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.

The world's first electric battery-powered submarine.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

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

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

"Portugal's Stonehenge" is made up of nut-like stones aligned with the heavens.

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

Earth's rocky history has rarely glittered so brightly as it does in this Spanish museum.

Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.

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

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

The earliest known map to show America, discovered by accident at a Paris bookshop.

This funky former tobacco factory is one of the most striking examples of Madrid's cultural diversity.

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

A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

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