Hidden in the hills is a mysterious stone structure, known only to a few.

A time-capsule monument reminding future generations of the importance of efficient and effective use of natural resources.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

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

The largest earthwork effigy in the world.

An ancient iron pillar in Delhi that seems to be rustproof.

Roots and stumps that lay inundated for two millennia are on display in Japan's city of three mysteries.

This hunter-gatherer architecture is believed to be the oldest religious complex known.

Natural catch-basin rocks covered in thousands of drawings spanning many millennia.

The meteor that sealed the fate of the dinosaurs landed at this site, one of the largest impact craters in the world.

Europe’s oldest natural human mummy.

Native Americans built this circle of stones, which was used to predict astronomical events.

A preserved oak tree about 3,500 years old found in Riga, Latvia.

Potential high level nuclear waste storage site for the next 10,000 years and beyond.

The closest thing to Mars on Earth.

A mysterious monument meant to be a guide into "an Age of Reason" was destroyed after an apparent bombing.

Home to Hollywood history and a very special salt crystal.

Hidden behind Lincoln's head is a 70-foot-long chamber containing enamel plates documenting American history, sealed in a teakwood box in a titanium vault.

Constantly maintained, this organ is playing a six-century long composition by John Cage.

A modern mechanical planetary system, part of a 10,000 year clock.

A musical composition 1000 years in length plays at the Trinity Buoy Wharf in London.

A clock designed to run with perfect accuracy for 10,000 years.

A failed piece of Orientalism has become the proud symbol of a community.

A small window on Via Piella offers a lovely and rare peek at Bologna's lost canals.