In the process of building the future cities, Information and Communication Technology (ICT) and Internet of Things (IoT) solutions are the key enablers. Although there are plenty of energy related data available in the cities, there are no established methodologies and validated tools to collect, integrate and analyse them so that they can support energy use optimization. In this context, the aim of this chapter is to present the Smart Cities IoT Platform. A “wireless telemetry cloud” over the city can be created, which facilitates the transferring of open data from the distributed sources (weather station, installed equipment, etc.). The proposed IoT Platform is composed of prediction models, scenarios and rules, as well as a database to store the data and results. With the Smart Cities IoT Platform, web-based applications can be created, customised to the specific characteristics and needs of end-users, including the fields of buildings, infrastructure, transport, generation and storage.