The City of Graz is one of the leading cities in the field of e- Government in Austria. It has developed an integrated e- Government platform that can provide uniform access to almost any kind of public service. In order to achieve the goals to provide unified access to virtually every single service and to minimize the effort necessary to bring new services online the City has developed an integrated e- Government Platform based on the utilization of an open source business process engine as the central controller. This paper describes the decision making process that had led to this architecture as well as key aspects of this system.