A subterranean house of worship carved right out of the bedrock.

A former French military respite turned jungle tourism hotspot.

A battle between nature and architecture in the Cambodian jungle.

The "Prussian Versailles" that is as glorious today as when it was built.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

Copenhagen's celebrated theme park and gardens.

Old Danish castle immortalized in Shakespeare's Hamlet.

Macabre astrological automaton clock dating to the late 1400s.

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

An old department store turned Nazi prison turned artist commune.

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

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

Louise Bourgeois' 30-foot-tall steel spider sculpture.

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

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

Ancient catacombs form the foundation for this Rococo orgy of a church.

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

One of the largest Roman settlements in Portugal.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

The corpse bride of Portugal.

The skyline of Montreal includes the silhouette of an unexpected fruit-shaped Canadian staple.

Montreal's giant farmer's market is a foodie's best friend, especially in the winter months.

The biggest museum dedicated to insects in North America, one of the largest in the world.

City law dictates that this mountaintop cathedral containing the heart of a saint is to remain the tallest building in town.