Sentilo is the piece of architecture that will isolate the applications that are developed to exploit the information "generated by the city" and the layer of sensors deployed across the city to collect and broadcast this information. The Barcelona City Council, through the Municipal Institute of Informatics (IMI), started in November 2012 a project conceived for define the strategy and the necessary actions in order to achieve global positioning Barcelona as a reference in the field of Smart Cities. Sentilo is an open source sensor and actuator platform designed to fit in the Smart City architecture of any city who looks for openness and easy interoperability. It’s built, used, and supported by an active and diverse community of cities and companies that believe that using open standards and free software is the first smart decision a Smart City should take. In order to avoid vertical solutions, Sentilo is designed as a cross platorm with the objective of sharing information between heterogeneous systems and to easily integrate legacy applications.