Found down a long dirt road, a sacred Mexican cenote and 18th-century hacienda remain hidden.

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.

An important Mayan religious and trading center dating back to 200 BC.

A flooded Mexican cave that hides a river beneath the water.

One man's fulfilled dream of living on an artificial island made of recycled plastic bottles.

Still standing despite its considerable slant, this tilted lighthouse has become a local symbol of resilience.

An island graveyard with spectacular views of the Caribbean.

Beach instrument turned bed and breakfast.

Underwater art project will double as a massive artificial coral reef to help regenerate the damaged ecosystem.

A small collection of iguana-infested ruins hides amid Cancún's bustling hotel zone.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

Near Birmingham, England three and a half miles of top-secret tunnels housed a World War II “shadow factory” and a Cold War nuclear bunker.

A quirky bookstore hidden beneath a sea of whitewashed Greek villas.

A spooky juxtaposition of caves and graves gives this legend-filled cemetery a particularly haunting vibe.

A reproduction of the famous prehistoric cave paintings is hidden underground at the National Archaeological Museum.

This fascinating and poignant museum chronicles every imaginable aspect of Spanish colonialism in the Americas.

Just like in Hollywood, Madrid has also a forgotten walk of fame.

The remains of the second-oldest zoo in Europe can be seen within these library gardens.

This species of wild goat stars in witchy legends and frolics among the park's eerie rock formations.

The unfinished final resting place of some of Spain's most prominent politicians.

A subterranean relic of the Spanish Civil War hides below this picturesque park.

This amazing abuela became a diehard metal fan late in life and an icon of Madrid's '80s rock scene.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.