Artifacts and posters illustrate the Nazi notion of a master race. Anyone who didn't fit into their model could be viewed as an enemy of the state, and sent to concentration camps. The Nazis required those they imprisoned to wear badges that identified their status: Political traitor, law-breaker, foreigner, homosexual, and a catchall, "Asocial" — [for] anyone who would not conform. A special badge, the yellow Star of David, went to Hitler's lowest of the low: the Jews.

Andreas: The Nazis believed that the German people were the "master race" — the toughest, the strongest, the bravest, the smartest. They said, "We should be running the planet; we just can't do it because of the conspiracy, the Jewish 'world conspiracy,' is in the way. And without them, if we deal with that conspiracy, then we will achieve our rightful status again.

The Nazis started putting their anti-Semitic ideas into action as early as April of 1933, when they organized a boycott of Jewish businesses.

Andreas: He specifically blamed one group, the Jewish people, for ruining things for everyone else.

Holger: For him, it was clear his scapegoat was the Jews. They were the source of all evil in Germany, and in the world, and he wanted to kind of get rid of that evil, and that's what he worked for.

Then in November of 1938 the Nazis led a pogrom against Jews throughout Germany. During Kristallnacht, or the "Night of Broken Glass," as it was called, Jewish homes, hospitals, and schools were ransacked. Seven thousand Jewish businesses were damaged or destroyed , and over a thousand synagogues were burned. And 30,000 Jews were arrested and put in concentration camps. This was a turning point from earlier economic, political, and social persecution to physical beatings, incarceration, and even murder. It was the beginning of Hitler's "Final Solution."

Today, Berlin's Topography of Terror exhibit stands on the rubble of what was once the most feared address in Berlin: the headquarters of the Gestapo secret police and the elite SS force. It was from here that government employees managed the Nazi state and dispassionately coordinated its most ruthless activities. The efficient and heartless bureaucracy behind Hitler's crimes gave rise to the expression "the banality of evil."

The evils of fascism were incremental. As its small evils became big evils, German society managed to be oblivious to its own atrocities. At first, concentration camps contained people who didn't conform. Then, they became forced labor camps. Eventually, the Nazis built death camps — which were located outside of Germany and therefore farther from public view. With what the Nazis called the "Final Solution," the entire Jewish population was targeted for extermination.

In total, approximately 6 million Jews died from Nazi persecution. 2.7 million of those died in death camps.

Auschwitz-Birkenau, in Poland, was the biggest and most notorious concentration camp in the Nazi system. Seeing the camp can be difficult. But Auschwitz survivors want tourists to come here, to try to appreciate the scale and the monstrosity of the place in human terms, in hope that this horror, known as the Holocaust, will never be forgotten.

As they entered these work camps, prisoners were greeted with a sign over the entrance: Arbeit Macht Frei — work makes you free. A cynical lie. Once inside, inmates were either worked to death or executed. New arrivals were sorted into two categories. Those who would be sent to the gas chambers immediately, and those who could work, [who] would live — at least a little longer.

Halls are lined with photographs of victims, each marked with dates of arrival and dates of death — inmates rarely survived more than a couple of months.

Up to a thousand people — each tattooed with an ID number — were packed into each of these buildings.

The gas chambers — where the mass killing was done — were disguised as showers. People were given hooks to hang their clothes on, conned into thinking they were coming back. (The Nazis didn't want a panic.) Then the inmates piled into the "shower room." In this facility the Nazis gassed and cremated over 4,000 people per day.