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

Located right outside of Vienna, visitors can take in expansive views of an ethereal forest.

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

A spherical "micro-nation" in the heart of Vienna.

One of the best collections of wax anatomical models in the world.

The topiary maze at the Habsburg hunting lodge.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

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

The resting place for anonymous victims of the Danube's dark waters.

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

Handsomely crafted representations of our round planet.

This former insane asylum now holds a pathological anatomy museum.

Macabre museum devoted to historical Viennese murders.

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

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

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

The beautiful baroque library of the Hapsburg empire.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

18th century anatomical amphitheater of the Royal College of Surgery of Barcelona.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

A former steam-powered mill from the 1800s is now an industrial park with a giant steel dragon slide.

A once-secret library of Freemason history in Catalonia.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

One of the most photographed buildings in a city known for its Modernista architecture is an abandoned squat.