An abandoned Incan construction project left behind a mysterious "doorway."

Mystic Incan rock piles three miles above sea level.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

The largest stone moai on Rapa Nui.

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

The enigmatic and seldom visited ruins of a Mayan city-state.

This singular broken monument, now housed in a museum, was the cause of a worldwide "Mayan Doomsday" phenomenon.

Statue of Edgar Hernandez, the first victim of swine flu.

The stoutest tree in the world.

Step into the cool deep past and unknown future of who begat who.

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

Location of the most powerful laser in the world, and the potential birthplace of tiny stars.

The world's largest Tibetan refugee settlement.

An Aztec temple, the largest man-made pyramid in the world, sits buried in earth with a Spanish church set on top.

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

Right angles in the forests of Panama.

These mysterious ancient stone spheres were created by a civilization lost to time and are now mostly lawn ornaments.

The world's second-largest sundial, made entirely out of stone.

Keshwa chaca, among the last handwoven Incan bridges, crosses Apurimac Canyon in Peru.

Home to Hollywood history and a very special salt crystal.

A set of ancient drawings in the desert of Peru that are so massive, many of them can only be fully seen from the sky.

Rusting ships sit in a desert where a sea used to be.

Centuries-old bridges grown from tangled roots.

The largest earthwork effigy in the world.