A note on Terezin:
Terezin, or Theresienstadt, was built between 1780 and 1790 by the Austrian Emperor Josef II and named in honour of his mother, Maria Theresia. It is a massive, star-shaped garrison town, built in northern Bohemia by the Austrians, in order to keep the Prussians out. Ironically the Nazis, almost two centuries later, realised that the walls, designed to keep a German army out, could also keep a non-German civilian population in.
Terezin was neither a model camp nor a concentration camp. The dubious honour of the first concentration camp goes to Dachau, whereas Sachsenhausen served as the so-called model camp. Instead, Terezin functioned as a transportation hub, through which the Jewish populations of Czechoslovakia, France, Germany, the Netherlands and Belgium were processed. Initially, Terezin was billed as a spa town, to which the Jewish populations of the occupied lands would be relocated. The Nazis did make a propaganda movie there, entitled The Fuhrer Gifts the Jews a Town, but the Nazi censors picked up on certain subversive tropes within the movie and it was never shown.
Whereas Terezin did do not have the same apparatus of mass murder that developed further east, it did ultimately became a routing centre for transports to the death facilities in the east - Treblinka, Majdanek and Auschwitz, amongst others. Then, after of the war, Terezin was used as a detention centre for many ethnic Germans, who lost their Czechoslovak citizenship and we expelled from the country during the period of post-war ethnic cleansing instigated by the Beneš Decrees.
Terezin today is a very depressed place. It was built as a model military town and in its day was a marvel of eighteenth century planning, engineering and ingenuity. However, its use as a place of incarceration by successive regimes in the 1940s has scarred the town. Today it is strangely forlorn, near-abandoned and futureless. Most visitors cannot leave the place quickly enough.
For further reading, Terezin features prominently in W.G. Sebald's masterful novel Austerlitz. Also, a good introduction to it can found in Madeline Albright's intriguing A Prague Winter: A personal story of remembrance and war, 1937 - 1948 which follows the dual narratives of her family (who were sent to Terezin) and the broader political developments in Prague before, during and after the Nazi occupation.