Digitalization has enabled infrastructure and cities to be “smarter”; the use of physical space and energy, the transmission of information, the management of users, assets and processes, the operation of businesses and companies have been progressively digitalized. The main challenges of a Smart City is its definition, scope and interconnections; there are different approaches to Smart City implementations that vary from collaborative multidisciplinary environments, the addition of Information and Communications Technology (ICT) within its physical fabric to the use of Big Data for higher abstraction decisions. This paper presents the concept of Digital as a Service (DaaS), where any complete digitalization can be implemented independently of its associated physical infrastructure in a Cloud environment; DasS would enable an interoperable Virtual Digital Infrastructure (VDI). In addition, this paper reviews the current Digital Systems, Transmission Networks, Servers and Management Systems. The next Industrial Revolution will be founded on Artificial Intelligence that will entirely replace humans by taking production and management decisions based on the Internet of Things (IoT), the Cloud, BlockChain, Big Data, Virtual Reality and the combination of digital and real infrastructure or city. Digital as a Service would be its enabler by providing the entire interconnection, integration and virtualization of its Space, Services and Structure (3S).