In this paper we describe an innovative approach to the design process of Smart City interventions. We tested it with participants enrolled in the Master’s Degree program in “Innovators in enterprise and public administration”: the objective of the Master was to stimulate the acquisition of technical and methodological skills useful in designing and implementing specific Smart City actions. During the "project work" phase, participants learned about a design method named SAM – Smart City Model - based on the Cultural Historical Activity Theory (CHAT). We present an overview of design criteria for Smart City projects, the description of the theoretical framework of Activity Theory, and our proposal of the SAM design model. We also present some examples of student’s “projects” and a more extensive description of one case study about the full design process of an App planned using SAM, for “smart health” vaccine management and monitoring services. The App was later published and made available to the citizens and was successful in attracting thousands of users. All the participants considered the model very useful in particular because it made possible to understand the interaction and solve contradictions between different stakeholders and systems involved. | Knowledge Management & E-Learning: An International Journal (KM&EL)