The first green space constructed on an elevated viaduct.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

The celebrated eyesore created by starry-eyed sweethearts.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

The unusual burial monument of Arizona's first governor.

A private collection of massive steel monsters guarding a Texas pipe works.

The only royal palace on U.S. soil has been a territorial capitol, a military headquarters, and a prison for a queen.

This blowhole is supposedly caused by a trapped monster.

A once-glowing grotto at the bottom of Waikapalae Wet Cave.