Sachsenhausen may not immediately strike you as 'day trip' material, but it is an important part of history. 40-50 minutes NW of Berlin (and cheap and easy by metro) you can visit the memorial of the harrowing chapter of German history. You will find the cynical 'Arbeit macht frei' on the entrance gate. Liberated in 1945 it was soon used again by the Soviets until 1961. Most of the buildings remain, including the haunting gas chamber and prison cells.
Free entry, closed on Mondays. A short easy walk from Oranienburg station and you get to see a very different part of Germany on the walk there.
*Not recommended for youngsters*
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