Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Venice's "Island of the Mad."

A striking 12th-century-style castle built on the edge of a cliff.

The enormous 250-room Vanderbilt mansion conceals hidden doors and secret passageways.

The final resting place of the poets Shelley and Keats.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

The 340-year-old house that inspired the classic Nathaniel Hawthorne novel.

A unique sculpture park that specializes in the huge and bizarre.

This expansive bridge in the Canadian wilderness was originally just built for friends.

This bright yellow relic is the final survivor of a short burst of seashell-shaped petrol pumps.

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

Designed by Buckminster Fuller, this relic of the 67 Expo survived fire and ice.

A 120-year-old legend concerning an empty circular patch in the North Carolina woods.

2300-year-old Roman road connecting the empire.

These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

The world of the ancient Celtic civilization explained through a bewitching 11 acre garden.

The only Bahá'í house of worship in North America and one of only a handful worldwide.

Though strikingly beautiful, Seattle's other railway station is now largely forgotten.

A stunning, abandoned limestone quarry in southern Indiana provided the stone to erect the Empire State Building.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

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

Site of a classic 19th-century physics experiment to prove the earth is rotating.

The final resting place for the remains of 143 Habsburg royalty.

Macabre headstones carved with winged skulls, dancing skeletons, and pithy reminders of impending death.