A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

Architectureal fantasy quarter of Rome.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

In a city that boasts four separate inclined cable railways, this is one of the busiest funicular lines in the world.

Dug as a secret royal escape route, the tunnel became a wartime bomb shelter and dumping ground for vintage cars.

These "anatomical machines" are only one of the many strange items in this Italian crypt.

A striking memorial recalls thousands of Bolognese men and women killed fighting fascists in World War II.

Legend has it this fountain built to symbolize the Pope’s power hides a strange secret concerning Neptune's manliness.

In the world's oldest university is a stunning 17th century anatomical theater carved from spruce.

Over 100 towers were built in Bologna during the Middle Ages, but only 22 survive.

Reminders of the Battle of Berlin still scar the railway.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

These former Nazi anti-aircraft towers offer a singular view of the north of Berlin in the summer, and a sanctuary for bats in winter.

One of the world's heaviest musical instruments towers within a popular urban park.

After a nearly successful attempt on Hitler's life, the conspirators met their fate in the courtyard of this Berlin building.

Berlin's beloved bear is immortalized at the Museum für Naturkunde.

Metro station with a claim to rock n' roll fame.

Cold war icon and onetime "hole" in the iron curtain.

A brush maker used his factory to protect blind Jews from the Gestapo.

A traditional U-Bahn station in Berlin gets a string of rather untraditional benches.

One of downtown Berlin's last reminders of its Communist past.

The world's first clock to use set theory as a measure of time required the invention of a new light bulb just to maintain its obtuse measurements.