I was recently watching Claude Lanzmann's epic, 9-hour documentary on the Holocaust, Shoah. During one portion of the film, Lanzmann interviewed several Polish villagers who lived near the Treblinka concentration camp. One villager said that the camp was only about 100 yards from where he plowed his field and that he often heard screams from the camp.
It seems paradoxical to me that, near the end of the war, the Nazis tried to hide evidence of the Holocaust yet, at the same time, they built camps that were so close to towns and villages. Was there any rhyme or reason to the camps' locations?
On secrecy see
https://www.reddit.com/r/AskHistorians/comments/dqr8kk/comment/f69c8ci https://www.reddit.com/r/AskHistorians/comments/dhjg5a/comment/f3p3bd8
Most extermination camps were not concentration camps and most concentration camps were not extermination camps, so the location of the average concentration camp didn't necessarily have to be influenced by the concerns of top secrecy due to extermination.
Sure, the Nazis didn't want the average Germans (if we're talking about the camps in Germany) to know what went on even in the "normal" concentration camps, but that was easy to prevent and the curious ones would have a chance to inspect the camps from inside anyway...
Now, when we come to pure extermination camps (such as Treblinka 2, which wasn't a concentration camp), they were on the occupied Polish and Soviet territories, needless to say the Nazis didn't care all that much if a few Polish or Soviet peasants knew something, they were not much of a PR factor.
The pure extermination camps were usually in some obscure spots, in the forests etc. and were small patches of land with a few buildings/graves/pyres. They would only become noticeable in the larger radius when the decomposing bodies in the mass graves would emit stench sometimes felt as far as 20 km away, or when the bodies were burned on pyres.
Auschwitz-Birkenau was both a concentration and an extermination camp, and it was even in "Germany proper" (Upper Silesia as defined by the Nazis), but it had a significant prohibited area around it from which the people originally living there were removed.
Moreover, it, like Majdanek, acquired its exterminatory function only after it was built as a concentration camp, such a function was not intended from the beginning and thus also played no role in where the camps would be built.