Two geological phenomena in one precarious locale: a towering stone window, and a deep blue void.

A tiny church on a man-made island in the Adriatic.

The final resting place of the great navigator, or maybe his brother.

The world's largest wooden structure.

An underground city of salt.

This iron and wood Civil War city-ship was the first vessel to be sunk by an electrically detonated torpedo.

Experience the hysteria of a 17th century witch hunt through goofy reenactments and wax dummies that should probably be burned at the stake.

The highest bridge in America was built for an almost unnervingly small amount of money.

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

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

This ancient Hawaiian henge may have been an early star chart.

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

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

Sitting in the basement of a castle, the largest wine barrel in the world is bigger than most apartments.

A restored Pittsburgh house of God has been converted to a marvelous house of suds.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

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.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

By day this New Orleans square is for pedestrians, but by night it is a kingdom of kittens.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

The farm where one of America's greatest leaders was raised is now a well-appointed landmark.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

California's own majestic geyser is powered by a subterranean volcano.

Once a favorite playground for the world's most illustrious guests, Hotel Nacional's secret weapons and bunkers reveal a more menacing side to its golden history.