These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

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

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

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

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.

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

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

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The celebrated eyesore created by starry-eyed sweethearts.

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

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

A favorite Paris bar for U.S. expats, including Gershwin, Hemingway, and James Bond.

World War II-era Nazi compound nestled in the Santa Monica hills.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

Elevated freight railway turned wildly successful urban park.

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

Remants of foundations, streets, and streetcar tracks inhabit the cliffs where a landslide occurred in 1929.

A hand-built folk art installation covered with messages of God's love.

The ghostly remains of an accidental sea.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

Macabre astrological automaton clock dating to the late 1400s.

Dramatic river bend surrounds a natural red-rocked pedestal.

On the Oregon coast there is a natural hole that seems to be draining the sea.