A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

This curious sculpture represents the perseverance needed to take to the skies.

Beneath the impressive baroque cathedral that rises from the center of Berlin lies the largest collection of Prussian royals in the world.

This obscene artwork on the side of a newspaper office pokes fun at a rival paper's former editor-in-chief.

At one of Berlin’s oldest churches, visitors can place mosaic tiles to help restore a medieval mural.

135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

The industrial architecture honors the laborers who brought the Exposition Universelle of 1900 to life.

Abandoned railway line circling the city of Paris.

Pitié-Salpêtrière was the dumping grounds for women who received the dreaded diagnosis of "hysterical."

The historic Masonic Lodge in which the first-ever female Mason was initiated.

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

The history of radiation is on safe display at the foot of a radiation science laboratory.

The remains of the medieval wall that once surrounded Paris with ties to the construction of the Louvre.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

The former home of France's controversial pop maestro is almost completely covered in ever-changing tributes and graffiti.

A simple plaque on the facade is the only reminder that the treaty ending the American Revolution was signed inside.

The largest medical and anatomical collection in France lies hidden from the public.

With a history of slaughter, feast, and famine, remnants of the pork industry decorate this area--even its church.

A curious collection of locks and keys.

Weird wax anatomical models reside here, as do other anatomical specimens.