Locals believe this abandoned ruin on the outskirts of Bucharest is haunted.

The legendary cliffside castle of three-time Voivode of Wallachia, Vlad the Impaler.

This once-derelict building is now one of the most beautiful bookstores in the world.

Once an opulent Art Nouveau hotspot, the Constanța Casino is one of Romania's most beautiful abandoned buildings.

One of Rome's most picturesque and original bridges was also a popular choice for Grand Tour artists.

An abandoned 17th-century baroque hunting lodge with a wonderfully strange architectural plan.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

2300-year-old Roman road connecting the empire.

A rebuilt Roman city that was once the largest Roman settlement in the region.

During World War II, Austria's oldest salt mine was used to store thousands of pieces of stolen artwork.

Two nations form a rare four-sided border at the peak of a mountain, philosophical questions result.

The world's largest historic armory was established by independent citizens to defend themselves from the wars of larger forces.

The amazing wonder cabinets of a very rich Austrian archbishop.

Archduke Ferdinand II's collection of rare objects is considered one of the oldest museums in the world.

A magnificent collection of imperial armor and weaponry.

A breathtaking viewing platform over the Alps.

A gift from Emperor Franz Joseph I to his wife.

This splendid tomb may look fantastic, but there's nothing in it...

This skeleton-filled altar piece served as a backdrop to one of the most iconic scenes in "The Sound of Music."

The shell of a medieval fortress offers commanding views of the area it once protected.

The world's oldest known salt mine.

American soldiers discovered Europe's best one-liner at the end of World War II.

An Austrian house of bones filled with hundreds of intricately painted skulls.