Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

Op-art architecture designed for happiness.

This Austrian museum celebrates the work of famous forgers and their inimitable imitations.

Macabre museum devoted to historical Viennese murders.

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

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

Bizarrely-painted church designed by a controversial artist.

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

Site of the 1889 murder-suicide of crown prince Rudolf and his lover Mary Vetsera.

In a crypt underneath this church lies a naturally mummified vicar whose story is surrounded by mystery.

Mozart's skull may be held in this collection, but definitive proof continues to elude scientists.

Terrifically morbid cemetary and site of famous Paracelsus' grave.

An unusual stroll through gentlemen's erotica demonstrates that pornography is timeless.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

This former charity hospital for elderly clergy houses some of Seville’s most treasured paintings.

The current seat of the Parliament of Andalusia was once the epicenter of the Great Plague of Seville.

Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

Notorious artist squat renovated into legal studios.

This former Masonic lodge has been transformed into part museum, part bar, all awesome.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

The former home of a mad diplomat is said to still be marked in bloody, arcane scrawls.

This massive library holds what was once the largest book collection in the world.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.