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

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

If you can look past the nearby sewer pipes, this urban sinkhole grotto is a mini-paradise.

At least seven hues of blue and turquoise make this freshwater lagoon unique.

A pilgrimage site where people ask Saint Dymphna to watch over those who are not of sound mind.

At the base of this tower, a plaque marks the original center point of the Netherlands.

A bridge that has seen many reiterations over its lifetime.

The world's largest bicycle shelter can hold more than 12,500 two-wheelers.

For over 100 years the most important physicists in the world have autographed this university wall.

An ancient octagonal weather station named for the eight Greek gods of wind.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

The hallucinogenic center of the ancient world.

Monasteries on rock pillars, once accessible only by frayed ropes.

This spectacular mosque houses the second-largest chandelier in the world.

A sinkhole and now a swimming hole, too, full of dazzling turquoise water.

Known as the "Valley of the Moon," this Jordanian wadi is one of the most amazing desertscapes on Earth.

A more chill but no less fascinating version of the famous ancient archeological site.

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

Located within one of Israel's most picturesque monasteries is also the country's first meteorological research station.

The maze-like transportation hub contains abandoned areas, derelict stores, and a resident bat colony.

As the Dead Sea continues to deplete, massive sinkholes open along its banks.

Descend 2,030 years into the past in an ancient tunnel built to support Jerusalem's most famous wall.

The location of the world's first telescope demonstration.