Smart cities are one of the most important 5G verticals due to their impact on people's life. The neutral host model is key for this vertical, specially to promote the infrastructure sharing between operators for a pervasive infrastructure deployment. However, it demands enhancements in today's virtualization technologies to support geographically scattered and resource constrained computing and networking elements (i.e., core data centers, edge computing point of presences, and far-edge servers at lampposts, etc.). This paper presents the virtualization enhancements developed within the H2020 5GCity project to support the neutral host model for smart city deployments. The envisioned virtualization technology demands security and technology extensions with a unified view of sliceable and heterogeneous devices and radio technologies (e.g., LTE, 5G, and Wi-Fi). In our solution, security is enhanced by deploying a robust compute node authentication, monitoring, and geo-tagging. In addition, wireless connectivity is extended via an innovative multiple RAN controller approach for the management and control of heterogeneous radio resources. In order to be validated, our virtualization approach is being deployed and demonstrated in the cities of Bristol, Barcelona, and Lucca.