An 18th-century Spanish watchtower made entirely of seashell and concrete.

A humid oasis combines recreation with exploration in a unique underwater cavern.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

A tribute to Ponce de Leon's supposed quest for eternal youth.

Town of spiritualists and mediums in Florida.

Possibly the most beautiful carillon in the world, set atop Iron Mountain in Florida.

This World War II relic let Allied pilots know they were entering neutral airspace.

A teddy bear sits on a chair watching the sunset from the mountaintop—just as the late Dan Clancy had done since childhood.

This modest plaza in Moneygall, Ireland has cashed in on its distant connection to the U.S. president.

Mortarless walls that stretch for miles are a lovely solution for creating grazing land in the harsh terrain of the Aran Islands.

A hugely vast Irish landscape of barren rock that stretches for miles.

This ancient Irish tower could easily have stood in for Rapunzel's prison.

This controversial Irish show cave is home to a massive formation known as the Great Stalactite.

The world's toughest modern Christian pilgrimage leads directly to the gates of Hell.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

An ancient neolithic tomb that only sees the sun twice a year.

The ancient tomb acts as a calendar that keeps perfect time.

Miniature art that tells an enormous story.

The installation’s official name, “You Who Are Getting Obliterated in the Dancing Swarm of Fireflies,” says it all.

The Jewish section of the famous Boothill Graveyard was abandoned for nearly 100 years.

A small literary museum remembers the life and works of the author of The Thirty-Nine Steps.