With the increase of their population, cities must adapt to offer more efficient services and better life quality. ICT and Internet of Things are among the technologies that enable smarter transportation, waste collection, energy and resource management, etc. But this does not come at no cost and new services arise through the collection and processing of a large set of distributed and ubiquitous data. This chapter discusses the requirements needed to achieve a Smart City, identifying the main technical challenges in the heterogeneity of devices, data, networks, protocols, and standards. To overcome these limitations, we propose our vision of Cloud of Meshed Cooperative heterogeneous Things (CoMCoT). CoMCoT targets to enable every traditional city's entity (node, user, and provider) to be exposed and consumed as a Service. Beyond traditional Cloud of Things (CoT) services such as data abstraction and mutualization, the CoMCoT provides more holistic functionalities by aiming at full interoperability.