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

A Lovecraftian altar of nightmarish bronze chairs sits ominously on a boardwalk in Puerto Vallarta.

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

These azure waters were thought to lead to the Mayan Underworld.

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

A lovers' beach, tucked below the surface of the island, provides a safe haven for romance.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

A 16th-century Andalusian palace.

Less a museum than a bizarre fantasy world created by artists and engineers.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

An eccentric collection of antique items shares space with a prop-quality witchcraft museum.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

Fortified medieval tower house with lovely roof garden.

The naturally mummified body of a peasant girl saint.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

Medieval torture techniques with a modern conscience.