After visiting hours, this picturesque waterfall is essentially turned "off" to be used for hydroelectric power.

Stockholm's narrowest alley is barely over two feet wide.

A rare surviving Victorian greenhouse designed specifically to house giant water lilies.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

One of the most photographed buildings in a city known for its Modernista architecture is an abandoned squat.

Week-long block party becomes a competition for the best decorated street.

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

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

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

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

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

Once an indicator of social class, the color blue has come to define this city on the edge of the Thar Desert.

Thousands of exquisitely carved stone water storage wells, hundreds of stone steps fill this exquisite medieval stepwell.

The 953 windows undoubtedly make this the world's most beautiful screened porch.

Paris' linguistic guide to the international language of, yes, love.

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.

This massive library holds what was once the largest book collection in the world.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

Notorious artist squat renovated into legal studios.

When the rain falls, this drain system turns into a musical instrument.

This medieval castle overlooking the Elzbach river looks just like it did hundreds of years ago.

The fairy tale castle of the "fairy-tale king."

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.