In the middle of downtown Brooklyn lies a 165 year old secret hidden right below the surface (closed to the public indefinitely).

The largest of London's subterranean rivers and once a mad, bad center of London life.

Surreal riveted sea forts once protected the Kent shores from German attack.

First LEED-certified gas station in the United States.

A Hawaiian stairway to heaven—that you can't climb.

Ride the subways of yesteryear.

Abandoned 19th century homes once occupied by naval officers, soon to be demolished.

A 30-acre garden inspired by the principles of modern physics.

England's oldest surviving hedge maze has been confusing visitors for over 300 years.

The largest stone moai on Rapa Nui.

A stunning silver lining to global warming's gloomy cloud.

Where giant ships go to die.

Cold storage for agricultural biodiversity.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

Spiral alpine structure provides an alternative experience of viewing the Matterhorn.

Cretean quarry suggests real-life site for ancient Greek myth of the man-eating Minotaur in his labyrinth.

Opulent downtown movie theater now houses cars as an indoor parking garage.

Thousands of exquisitely carved stone water storage wells, hundreds of stone steps fill this exquisite medieval stepwell.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

The ancient tomb acts as a calendar that keeps perfect time.

An abandoned facility that has become a place of ritualistic satanic worship, or so rumor has it.

The closest thing to Mars on Earth.

Lost subway station nestled beneath Toronto's busy commuter line.

Secret Swing.