I'm trying to write something smart, but honestly, I hate history. Mostly because I was guiding tourist to the museum since I was 7, and we never learned about the city history. It's because of the Polish school system when we learn from Faraons to half of the WWI every 3 years.
I recently took my SO to "the bunker" (Place on the next street, here is google maps location: 50.026725, 19.291366 street view mandatory) and remembered few of the stories my grandmother told me. I assumed they are kind of urban legends or stuff people made up to feel better and ignored it when I was a teenager. I also read a random askreddit post and someone mentioned "Monowitz", we talked a bit and I was quite interested, then forgot about it. Monowitz is the name of the village I used to live, and I never realized that this place was "Auschwitz" too.
Back to the bunker trip, we started talking, and I told my SO all the weird stories, she told me to post here for clarification or guidance where to look.
The question list:
The Bunker, what for, who build it, was it important, is it possible that it has a 10km tunnel under the city with hidden guns and gold? There is a German-speaking trip every year, the bust stops next to it, they watch and take photos for like a 3-4hours and disappear. Usually around 20 people.
Monowitz or Monowice or "Auschwitz III" what happened there? Any information on local people? I know only that my grand-grandparents were expelled from home and Germans made "shower" in there, not this Auschwitz like, the normal one if we can call anything normal here.
If you have any question to someone like me, not sure if it's interesting to you how the city looks like now or something, feel free to ask.
Let me try my hand at the second question; Monowice/Auschwitz III.
Monowice was the last portion of Auschwitz. Auschwitz was a concentration camp built to hold Polish prisoners and dissidents, first opened in May 1940. As the Nazi's plan to exterminate Jews was finalized, it began to be used to hold Jews, though it also held Romani(gypsises), Poles, POW's, and religious and political dissidents. There was three main camps in Auschwitz, though there were up to 45 smaller camps.
Auschwitz I: Largely used to hold Poles, functioned as a concentration camp. It was used to hold prisoners, provide slave labor, and kill individuals or small groups of people who were deemed a threat. Auschwitz I had a gas chamber and crematorium. Medical experiments were also carried out at Auschwitz I, and many prisoners died.
Auschwitz II: Perhaps what people most imagine when they think of Auschwitz. Auschwitz II was a combination of an extermination/death camp, and a concentration camp. All prisoners underwent "inspection". Those deemed fit for labor were forced to work, while those deemed unable to work(the elderly, sick, or young children) were gassed.
Auschwitz III: Another concentration camp, built last and used for a source of slave labor. We will discuss it at more length.
Let us first talk about the purpose and building of the camp. The camp was built in cooperation between IG Farben, a German chemical company that widely used slave labor, and the SS. The camp was built around a chemical plant, to be used for the creation of synthetic fuels and rubber. The location was chosen in part for its flatness, connections to roads and resources. Of course, the main reason was the existence of the original Auschwitz camps nearby. These were a source of slave labor. Now, on to what might have happened to your great-grandparents. IG Farben itself purchased the land from the occupying German government, with the remainder seized from Polish residents(which might have included your family).
The inmates of Monowice numbered about 12,000 at any one time, mostly Jews. Monowice was designed as a workcamp, not an extermination camp. That being said, workers were often worked to death, or died or malnutrition, starvation or diseases. If that didn't kill them, workers who could no longer labor were sent to gas chambers or killed in "hospitals".
On January 18, 1945, those prisoners healthy enough were sent on a death march to another camp near the former Czech border. Auschwitz was liberated on January 27, 1945, including Auschwitz III.
Probably the most famous prisoner at Auschwitz III was Elie Wiesel.