The most visited, and possibly most controversial, museum in Germany.

Constructed on the ruins of a convent, this tower saved countless lives.

Dedicated to the European Sinti and Roma peoples murdered during the Holocaust.

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.

A towering monument to war, located on a beautifully peaceful hill.

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.

This water-tower-turned-high-end-apartment building was once the site of an early Nazi concentration camp.

Berlin's old airport.

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

Tiny memorials honor individual victims of the Holocaust.

Once home to one of the oldest banks in the world, this building is also where Marco Polo's famous travelogue was written.

The tallest city hall in the world offers an excellent bento box.

Nelson Mandela lived here with his family from 1946 until his arrest in 1962.

The stunningly blue waters of these beautiful caves also have a violent past.

This grisly effigy displays an early Christian martyr who was skinned alive and beheaded.

This amazing medieval fortress stands atop a promontory along the famous Cinque Terre.

This cave overlooking the Indian Ocean has been turned into a shelter and makeshift museum.

This granite mountain is the largest rock in Africa and the second-largest monolith in the world.

A beautiful viewpoint on the Garden Route overlooking a naturally-occurring outline of Africa.

This 14th-century temple is also known as the "Temple of the Golden Pavilion" for its gorgeous gilded reliquary hall.

One of the most well-preserved castles in Italy also contains a rare medieval example of a port fortification.

This enormous monument is one of the most iconic structures in Tokyo, rudely nicknamed "The Golden Turd."

This subterranean oyster house has been the pearl of Grand Central Station since 1913.

L. Frank Baum wrote part of the "Wizard of Oz" series in this wooden Victorian beach resort.