I’ve never been to the Holocaust museum there. But I’ve been to Yad Vishem and toured Auschwitz and Birkenau.
The latter was particularly impactful. Unlike Auschwitz, it’s not really a museum with exhibits. It’s just an empty camp. When I saw it, it was late in the day after all the tourist buses had left. Virtually all visitors come via bus from Krakow. I was with my Polish girlfriend at the time and we drove there.
It was just us, no one else, walking through that camp. It was silent and eerie, and unchanged. It could have been the summer of 1945.