A nearly unconquerable island-fort in the Indian Ocean.

A giant portrait of an ancient king looms over the river.

The tallest residential building in Africa is an unsettling Brutalist monolith.

A Roman monument to their own civil engineering prowess.

This "Palace of Purification" has made many film appearances as a dark and sinister headquarters.

An old trolley bridge was converted into a breathtaking garden bursting with colorful flowers.

An ancient Egyptian temple in the middle of Madrid, Spain.

The world's most elegant power lines.

Super-heavy Nazi architectural experiment.

A collection of unique outdoor sculptures surounded by the beauty of nature.

The enigmatic and seldom visited ruins of a Mayan city-state.

Venice's island of the dead.

The Jesus tree of Malta bears a striking resemblance to Christ on the cross.

Monasteries on rock pillars, once accessible only by frayed ropes.

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

An accidental trick of light casts the perfect shadow of a pilgrim of the Camino de Santiago against the cathedral wall.

A classically inspired temple in Redwood City.

Possibly the most beautiful carillon in the world, set atop Iron Mountain in Florida.

Climb the dead electric pylons of Messina.

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

David Sedaris called it "The greatest shop in the world."

This replica of the Greek structure is in the heart of Nashville.

Massive puppet-automaton machines created by French artist collective Machines de l’Ile.

Tiny castle in the middle of the Rhine made you pay to pass.