Cities have to increasingly consider topics such as climate change and digitalization. Ideally, the digital transformation should support becoming more climate-friendly. New digital services are being developed and made available to citizens. However, it is often difficult to test ideas for new services from both a technical and a user -centric perspective. Reasons for this are, among others, that existing technical infrastructures provide a complex environment where deployment is often time-consuming. Furthermore, certain qualities such as performance or data protection have to be ensured, which is something a prototypical solution might not be able to offer. We are developing digital sol utions for a climate-neutral smart city district, and one of our main challenges is that the area is still under construction and no technical infrastructure exists yet. Therefore, we developed a mock environment for a digital ecosystem in which we can easily test new ideas and early service prototypes. In this publication, we share our experiences on how we used this environment in a hackathon event and provide results from the participants who used our smart city district simulator. We provide three concrete examples of different implementations and discuss how our technical solution support s the development of new digital solutions and how it might also be a solution for other cities. As we would also like to apply the technical environment in other contexts, we then describe one concrete use case in the area of heavy rain and elaborate what this means regarding further development of our simulator and the technical infrastructure.