In his book, KL: A History of the Nazi Concentration Camps (New York: Farrar, Strauss and Giroux, 2015), Nikolaus Wachsmann persuasively shows that the concentration camp system was no secret to many Germans. The extent to which civilians knew about specific camps varied greatly across the German lands. In Berlin, for example, the early camps in spring and summer of 1933 were typically established in existing facilities that tended to be in urban centres, such as Mitte and Kreuzberg. These facilities were closely situated in densely-populated areas.

Contrary to some immediate post-war responses to the discovery of death camps in Europe, the concentration camp system had been discussed in local newspapers as early as 1933. As Wachsmann writes, "The regime did not hide the early camps' existence. On the contrary, the press--soon coordinated by the new rulers--carried countless articles, some initiated by the authorities, others by journalists themselves...Several historians have suggested that most Germans welcomed such reports because they supported the camps and the regime's broader aims." (Wachsmann, 64).

If you are interested, I would recommend Wachsmann's book. It is comprehensive and cogently written. He has explored a wealth of archival and manuscript sources to produce an excellent book on this topic. I hope this helps.