The Internet of Things (IoT) presents opportunities for cities to provide a multitude of new services to their citizens. Such services need to be procured from suppliers. In order to facilitate procurement, a marketplace is suggested that enables public officials to select and evaluate suppliers of relevant services. This thesis investigates requirements for such a marketplace. Through a number of interviews with stakeholders and through extensive literature research, the thesis identifies relevant functionality and obstacles. These are summarised in an analytical framework and opportunities for future reseach are identified. Among key requirements for the marketplace, three themes are identified: (1) facilitation of procurement of open systems from several suppliers to one and the same buyer; (2) quality assessment and performance evaluation of suppliers and their services; and (3) decision support for stakeholders, including citizens and end users. Research literature and empirical findings related to these three themes are investigated in detail.