Research on the history of computing often needs to adopt experimental archaeology methods: the rebuilding of old hardware and software requires us to proceed by hypothesis and experimentation. This is one of the key assets of the HMR project, whose main goal is the study of Italian computers from the Fifties and Sixties. The results obtained by the HMR research are made accessible to the public through exhibitions and workshops held at the Museum of Computing Tools of the University of Pisa. The visitors of the Museum, mainly students from middle and high schools, are introduced to the basic concepts of computer science through fascinating old machines. The paper reviews some of the results of the HMR project and presents how historical computers, either preserved at the Museum or rebuilt by HMR, are shown to the public to teach principles and mechanisms of computer science.