The historical GIS is, without any doubt, a powerful means of communica-tion of historical phenomena for the public and also of collecting georeferenceablehistorical source through crowdsourcing activities, but the complexity of the datamodel underlying a GIS can also distance the public from understanding the com-plexity of the phenomena themselves. From this point of view the role of the DigitalPublic Historian is essential: not only will he/she have to be able to construct a GISwith a methodologically correct data model, but he/she will have to find the rightways of communicating it in order to make the GIS an effective tool of understandingand sharing the past.