When in Belgium I went to Breendonk which was a Nazi prison camp (torture but no mass exterminations). It was a cold gray day with a bit of rain and even with the passage of time it was awful. My male Belgian friend and I were nearly in tears when we left.
I visited Dacchau on a date... Yes, my soon to be second husband and I were stationed in Germany but not co-located. I worked a wonky schedule, but one ot the times our days off coincided we went to visit some of the historic sites in Germany, we felt it was important enough, in fact very important. It was powerful, and yes quite a downer. But I will never, ever forget it. About 25 years later I was in Washington DC with my two oldest and the fiance of the oldest, and we ended up having to stay til Monday and had nothing scheduled on Sunday. I told the kids to choose, and they chose the Holocaust Museum. That was one of those "damn, I did good moments." It too was very moving, very powerful.