Rebuilt remains of a temple to Roman god Mithras.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

This dramatic landscape hidden on the Isle of Skye looks as though you've stepped into the magical realm.

Northern Ireland's Brobdingnagian stepping stones.

These fantastically named natural pools look like something out of a Scottish myth.

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

The sign at the garden gate reads: "These Plants Can Kill."

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.

These aggressively sustainable art homes look like something out of 1970's science fiction.

This otherwise unremarkable ski town building marks the site of Butch Cassidy's first robbery.

It would be easy to walk past this unusual piece of art and have no idea it pays tribute to the odd life of a real chicken.

The site where a nuclear bomb was lowered over 8,000 feet underground and detonated as an experiment in natural gas extraction.

The remains of the dam that unleashed a 15-foot wall of water on Denver.

The world's largest key collection features keys to the White House, Frankenstein's castle, and Hitler's bunker.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

The final resting spot of the Colorado Transportation Department's beloved unofficial mascot.