Sachsenhausen Tour.

From the very start of their rule, the Nazis built a network of prison camps across Germany — first to lock away political opponents, then, as the years went on, anyone who didn't fit their idea of a "pure" German society. Sachsenhausen, just north of Berlin, went up in 1936 as one of the earliest of these large camps.

Built as a model camp, Sachsenhausen is where the Nazis tested and refined their system of oppression and murder before rolling it out elsewhere.

This tour follows communist prisoner Harry Naujoks through the camp's history. We start at Berlin Hauptbahnhof and take the train north to Oranienburg, talking on the way about the Nazis' rise to power and how Naujoks became one of their earliest victims.

Once inside, we look at the camp's triangular layout and its surrounding wall, walk past what's left of the massive Watchtower A, and step into Barrack 38 to see how Jewish prisoners lived day to day. You'll hear how Naujoks worked the camp kitchen to organize communist resistance from the inside, and how he fought — often at great personal risk — to keep fellow prisoners out of Station Z, the camp's execution site, and away from the Gestapo's feared special prison.

We take the train back to Berlin together at the end of the tour.