In the paradigm of the Smart City, cities are embracing new digital technologies and data innovation to redefine their relationship to citizens and enterprise. Increasingly, cities are developing visions, strategies, and related digital masterplans and action groups with which to coordinate these efforts. The European Horizon 2020 funded OrganiCity project explored a new model for providing access to all citizens to collaboratively develop and test their ideas for managing and improving the urban environment using data. The people centred and data driven approach of the OrganiCity project developed an Experimentation as a Service (EaaS) model across 13 cities and with 43 experiments. In this paper, we describe the 4 key service pillars that emerged through designing a platform to enable experimentation and the associated engagement practices required to facilitate testing in a city. The service pillars are: systematic experimentation, co-creation, federated ethics & privacy, and management of liability & Intellectual Property Rights. The EaaS approach provided a low-risk service blueprint for city authorities to democratically source, test and support scaling-up innovative solutions to their city challenges. Analysis of experimenter’s projects highlighted the importance of shared infrastructure for reducing the barrier to entry for accessing the digital tools, but more importantly highlighted the investment required, and value of, the human resources required to facilitate the process of experimentation.