On the Conglomerate, Gordon Smith was discussing his impressions from visiting Auschwitz. (I also recommend reading the original post he cited, and some of its comments.)
I weighed in in the comments on my experience visiting Dachau:
One of the best Holocaust museums I've ever seen was at Dachau. In the main building, which has survived, there is a series of exhibits on the history of the period. Starting from about WWI, the exhibits slowly snake around the large room, showing how bit by bit over time things would change. The changes were so slow and incremental, and often each one seeming so reasonable in its own context, it was hard to realize, except once at the end, looking back across the room, just how mammoth the departure from reasonable things had come to be.(The exhibits were all described in German, but there was a $30 book with the English translations. As a student traveler such an expenditure was quite a luxury, but it was definitely worth having. The book contains pictures of the exhibits along with its descriptions, so it's like having a portable version of the museum.)
Much is gone at Dachau. The barracks are mere foundational outlines, with just a few reconstructed. The creamatorium is still there, though, and still in operation as a building (not as a creamatorium, but the groundskeepers use the basement office).
But much of the impact of visiting Dachau comes just from being there, of being in a place where so many went in and never came out, while you yourself are able to pass in and out of those giant "arbeit macht frei" gates as freely as you want.
The other writer also described the emotional state one has before travelling to a place like this, noting how nerves were frayed and he and his companion were sniping at each other. I was travelling alone on my Dachau visit, but on the bus ride over there were several other Americans to commiserate with somberly. We were already in quite a mood: TWA Flight 800 had just blown up, and news about it was slowly leaking into Germany. It was a tragedy we felt connected to in some way, although it was hard to explain why, or to even know how to feel. We weren't there, and we didn't know anyone who was, but somehow it felt like we had a right to be profoundly sad.