Here are a few fun facts about Auschwitz. They originally claimed that 4 million people died there, but that was mathematically impossible since there were only 4 crematoria and no mass graves, so they lowered the number to 1.1 million, but the 6 million total never changed. In reality Auschwitz was a work camp with a soccer team, theatre, a swimming pool, and other amenities.

Also it's impossible to kill masses of people with gas, except by horrific methods employed by the jews against the Russian/Ukrainian people before, during, and after WW2. In the US, gas execution was briefly used for capital punishment using an airtight chamber, but the results were still horrific and inconsistent and it was banned.

But even if you accept every lie you've ever been told about the holocaust, ask yourself why you've never heard of the Holodomor. 

 Oh and also there were no traces of zyclon B, a delousing agent used by the evil Nazis to save the jews from typhus, on any shower walls.

And I don't want to leave off my personal favorite - there's an actual giant chimney in Auschwitz, to this day right now, that's not connected to anything. Literally just a giant brick "chimney" that was constructed after the war by poor craftsmen, and it's still there, and it's definitely not part of the "official tour".