A great place that we went to in York was DIG, the kids loved it. It was all about archaeology. The tour lasted 1 hour, first the guide talked a bit about archaeology, then we got plastic trowels and they had four bits you could dig in - Roman, Viking, Middle-Ages, Victorian. The guide talked about what you uncovered. Then to finish he showed you lots of different bones and things they had found. It was great fun - especially the digging bit.