This shallow cave got its name from copious amount of human bones found inside.

A statue in the center of Dublin dedicated to one of their favorite sons of rock & roll.

The somber sculptures commemorating Irish Famine on the river Liffey in Dublin.

The handiwork of a underdog clockmaker who solved an impossible problem for an Empire, and forever revolutionized seafaring.

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

Elevated freight railway turned wildly successful urban park.

Touching mementoes from those who didn't make it back from World War I still hang in one of New York's oldest bars.

Meet your friends, marry your true love, or tell your enemies to kiss your butt under this historic Pittsburgh timepiece.

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

A science teacher's dream.

Mary Kelly was last seen here before she was murdered by Jack the Ripper.

These delicate sand pyramids look like naturally occurring gothic spires.

A geological mystery on Camelback Mountain.

A portion of the old Pirates stadium over which a defining home run once flew still stands even after the rest of the stadium was torn down.

The house that Frank Lloyd Wright "(shook) out of his sleeve at will" at the age of 86.

There aren't too many operational funiculars around, but Pittsburgh has two!

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

The largest university building in the West is a gothic masterpiece containing dozens of theme rooms based on different countries.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

Mysterious rocks that ring musically when struck.

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

The only structure left with direct ties to the Salem witchcraft trials of 1692.

Hell on Earth is actually a small town in Michigan where anyone can be mayor for a day.

A park and memorial dedicated to the victims of the deadliest school massacre in American history.