A half-mile-long stretch of medieval forts built after a devastating pirate attack persists amid the modern port city.

Now a memorial to merchant sailors and Titanic victims, this medieval church was destroyed by bombing raids in 1940.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

This raised bulls-eye visible from space was the subject of an intense geologic controversy.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

2300-year-old Roman road connecting the empire.

The beautiful, ornate weather station is the most popular geocache in Salzburg.

This strange statue features a bust of the famous composer plopped atop a woman's body.

Terrifically morbid cemetary and site of famous Paracelsus' grave.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

Island wonderland for communist autocrats.

A muddy alien landscape that is home to rare species of exotic plants.

Conspiracy theories and occult legends surround this mysterious natural rock formation.

One of the oldest churches in Romania is believed to have been built on the site of a pagan temple.

This fairy-tale castle would make Dracula (who is said to have been imprisoned there) jealous.

Moss and stone turn this waterfall into an otherworldly liquid veil.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

A museum dedicated to a secret military hospital hidden beneath a castle in Budapest.

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

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.