Every equinox this Maya pyramid puts on a spooky ancient light show.

In the middle of an extremely unforgiving and desolate high desert is the most secret military facility in the world.

Once the most densely populated place in the world, this island is now a ghost town.

A battle between nature and architecture in the Cambodian jungle.

Hoax, mistake, or evidence of dinosaurs in human times?

The largest earthwork effigy in the world.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

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

Giant naked man on a hillside.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

An Ethiopian "Jerusalem" featuring a church hewn out of a single rock.

A remote forest of stone pillars along the Lena river.

A salty cave excavated by elephants and the location of a deadly disease vector.

An autonomous republic of Orthodox monks.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

This sword isn't waiting for a king to pull it out. It was placed there by a saint.

This "floating island" plateau sits 7,671 feet above the forest floor.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

This "preacher's pulpit" once used for pagan ritual, is home to a new, and dangerous ritual.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

Charles Babbage's proto-computer, painstakingly brought to life.

Walk 2,300 feet above the ground on the "Troll's Tongue."

Northern Ireland's Brobdingnagian stepping stones.

The underground sanctuary of a mysterious ancient cult.