My favorite museum experience ever was at Chicago's Museum of Science and Industry in the early 00's where they had this whole room that was just wood blocks, a little plastic tub running like a creek, a few little water-directing mechanisms and a couple water guns. No goal, I dont think it was even teaching anything, it was just me and 8 other kids. When I first got there some kid was telling everybody how to use everything and what little project he was working on and how they could help, basically like a little foreman. I helped and had fun with everybody for maybe 15 minutes until he had to leave and by then I had been there longest and just naturally ended up taking over as "foreman" until it was my turn to go and I told another kid everything that was left to do. It's a very important dynamic you experience a lot in life, and that exhibit taught me it naturally in half an hour.
It's such a shame to see how many of these learning museums are now basically having these kids just walk from point to point and read and maybe play something that would have been bad as a flash game. The Seattle one (forget the name) I went to last year had a decent number of physical exhibits (which I still enjoyed as an adult) but none of them had any social element. Ironically, the screen games were all very poorly maintained.