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

The oldest working mechanical clock in the world.

Regency-era excess on the English Coast.

The oldest of Venice's plague quarantine stations, designed to keep the medieval city safe from disease.

Go inside to really appreciate this 500-year-old technological masterpiece.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

The oldest operating pharmacy in the world features 800-year-old recipes.

Northern Ireland's Brobdingnagian stepping stones.

Striking occult iconography on a medieval German church.

Largest cave system in Africa.

A snapshot of the city's fascinating voodoo culture.

This metallic stampede sits frozen on a Washington ridge yet the artist's vision is still incomplete.

Experience a charming 1930s version of "infotainment."

Orcas on display and in the water.

A bike being "eaten" by a tree is the real Vashon legend behind popular children's book, "Red Ranger Came Calling."

The Beaux-Arts aquarium boasts a vast collection of saltwater and freshwater fish on an island in the Detroit River.

Island where motor vehicles are banned -- home to the only carless highway in the United States.

The fifth-longest suspension bridge the world, connecting one Michigan peninsula to another.

Welcome to old Florida, where a 1940s mermaid show is still enchanting visitors.

Town of spiritualists and mediums in Florida.

The largest island on the great salt lake is home to curious creatures and strange stories.

A museum dedicated to the alleged Roswell Incident.

The only arched bridge made of stone on the entire Mississippi River.

The first American department store, and home to the largest operating musical instrument in the world.