This charmingly homemade amusement park has been growing for 40 years.

World's first "penitentiary," meant to be humane, drove men insane.

Two stunning 17th-century libraries and a cabinet of curiosities.

An underwater city for the dead.

An experimental, automotive replica of Stonehenge.

The internet as provided by a James Bond villain.

The largest hewn stone in history.

North Korea's massive "hotel of doom."

The explorer Captain Cook may have named it White Island, but the Maori call it Te Puia o Whakaari – The Dramatic Volcano.

A precariously perched golden rock defies gravity and brings pilgrims from across Myanmar.

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

One of the world's steepest streets seems to have houses sliding down it.

Remote, volcanic island that Darwin, Hooker, and the Royal Navy shaped into a thriving, artificial ecosystem.

Ghosts of France's colonial past.

The world's largest statue of Mao Zedong looks out over the city where he discovered Communism.

China's very own Atlantis is an ornate dynastic city resting at the bottom of a lake.

The legendary building that needed ghostly approval before being built.

Huge concrete structures designed as an early warning system for Britain to detect enemy aircraft.

Collapsing castle on the Hudson river was once the storage site of military surplus business.

A marvel of Byzantine engineering under the streets of Istanbul.

Gleaming self-built castle towers made from beer cans and inspired by "Vitamin Mary Jane."

Roadside collection of 65,000 signs.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

First known as the "Sample House," this construction mash-up was meant to be a living catalogue of building styles.