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

An exquisite Baroque church in Vienna's old town.

This museum promotes informed contraception by documenting its often secret past.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

Legends surround an ancient tree trunk riddled with nails for good luck.

Baroque celebration of the end of the Great Plague of Vienna.

The topiary maze at the Habsburg hunting lodge.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

This former insane asylum now holds a pathological anatomy museum.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

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

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

The beautiful baroque library of the Hapsburg empire.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

One of Madrid's oldest trees, with a long and colorful history, resides in El Retiro Park.

This lucky bronze frog was gifted to Madrid by a casino.

The only urban monument in the world designed by the great surrealist painter Salvador Dalí.

A whimsical brother of the nearby Fallen Angel statue takes the falling part quite literally.

Commonly acknowledged as the only public monument to the Devil himself.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

The location of the world's first telescope demonstration.

Hidden within a Netherlands crater is a stone bed that lets those who lie in it see the sky as a curved surface.