An abandoned NSA listening post on Berlin's "Devil's Mountain."

"The most colorful grottoes of the world.

A stairway to heaven, or to nowhere at all.

A tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.

This "floating railway" is one of the world's oldest monorail systems.

A 12th-century fortress containing some of Berlin's oldest buildings.

A unique Holocaust memorial tells the personal stories of the Jewish residents exiled from greater Berlin.

Someone loved this song enough to carve all of its lyrics onto a tree trunk in a Berlin park.

A church filled with the bones of hundreds of virgins martyrs—or so they say.

An intricate and amazing house built by architect Karl Junker.

When the rain falls, this drain system turns into a musical instrument.

Home to 10,000 medical specimens including the remains of Rudolf Virchow's extensive collection of pathological specimens.

The patron saint of spinsters grasps a container of dried blood.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

From toys to kettles to scientific instruments, this German museum celebrates the beauty of 20th century design.

A striking 12th-century-style castle built on the edge of a cliff.

This World War II bunker now survives as a documentation of the Nazi regime and war crimes.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

Skeletons dressed in extravagant 18th century royal costumes cavort in the aisles of this German basilica.

Berlin's natural history museum houses the world's largest mounted dinosaur and the late beloved polar bear Knut.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

A sprawling Baroque park with 300-year-old hydro-pneumatic waterworks.

A fascinating insight into daily life in the Eastern Bloc.

Gardens representing parts of Asia, Europe, and the Mid East are tucked away among the Soviet-style buildings in East Berlin.