This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

The remnants of an early American attempt at missile defense.

A massive underwater sinkhole made famous by Jacques Cousteau.

The meteor that sealed the fate of the dinosaurs landed at this site, one of the largest impact craters in the world.

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

An ornate tower shows off a local artist's architectural flair.

A gravity-defying "devil's bridge" that has a surprising architectural feature for its stability.

Massive crater in central Oregon.

This massive mushroom has spent centuries eating its way across a huge swath of Oregon.

Astonishing collection of helmets, scientific instruments, and medical models.

An island filled with hundreds of hanging, decomposing, decapitated dolls.

Living trees form the structure of an open-air palace.

This "preacher's pulpit" once used for pagan ritual, is home to a new, and dangerous ritual.

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

Japanese island famous for poison gas and fluffy bunnies.

Giant, pink stuffed rabbit on an Italian mountain.

Sparkling, calcite-covered skeletons of children who may have been sacrificed to appease an angry god.

Last residence of H.P. Lovecraft featured in his story "The Haunter of the Dark."

A stunning bridge that appears as if it's lunging to the shore, and has a legend of a devilish architect.

Unrepaired walls from a 1920 anarchist bomb attack.

A 14th century bridge built as a fortress, where the devil lurks on one of its towers.

A stunning, abandoned limestone quarry in southern Indiana provided the stone to erect the Empire State Building.

The Gaudí-inspired building that was the start of Terrassenc modernism.

The United States Capitol's former columns still stand.