In this tiny Iranian town playing on the roof isn't just encouraged, it's the only place to go.

This abandoned Belgian fortress is purposefully being left to nature.

Sculpture designed by Turkish artist and professor Mehmet Ali Uysal.

This giant urban staircase was built to keep the city's brave fighting men from getting waylaid in the red light district.

Devoted Buddhists can earn enlightenment in the next life by crawling through this symbolic nostril.

The small alleys in Lübeck's Old Town are a result of medieval urban sprawl.

This peculiar museum offers hands-on interaction with seemingly intangible principles of mathematics.

Steaming blood-red hot spring from hell.

This beautiful Japanese garden is a memorial to the samurai who literally wrote the book on business as martial art.

Caves full of Buddhist statues, incredible rock formations and a deserted lagoon.

This pair of small sea rocks has been "wed" using rope and ancient Shinto tradition.

An abandoned lighthouse awaits its destiny: being buried under shifting sand.

Launchpad for the US military’s dead mouse operation to battle millions of snakes.

Located on Guam's south shore, this small cave is named for an ancient and powerful Chamorro Chief.

Famously misunderstood wonder of the ancient world

Catacombs turned marketplace.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

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

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.

According to the Guanches, the aboriginal people of the Canary Islands, the king of evil lives inside this volcano.

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

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