An extraordinary mechanical calculator designed by the mathematician and philosopher Gottfried Leibniz.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

Residing along a busy thoroughfare, this sculpture urges passersby to consider the future.

Once the tallest building in the world, this abandoned church is now a monument to the destruction of WWII.

This wooden hotel is a temple to German sustainability and forest conservation.

This contentious squat has stood through fire, violence, and government intervention as a hotbed of leftist protest.

Hamburgers are intensely proud of their tunnel beneath the river.

The world's most active stratovolcano is almost always erupting.

Thousands of well-dressed mummies below a monastery.

This mosaic-lined medieval church was built by the world's first admiral and still holds mass in ancient Greek.

Why a column on the entrance is inscribed with a verse from the Quran is one of Sicily's many mysteries.

This bridge was constructed from the rubble of the infamous Bastille.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

France's most famous cemetery, with some of its most curious tombs.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

The final resting place of soldiers' loyal canine companions.

A scattered trail of street art adds a pop of color to the city's stark structures.

"Respectful to the dead, safe and sanitary to the living, dedicated to the Genius of Memory..."

A much-loved sculpture depicting the hero of a 1956 anti-Soviet uprising.

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