Summary: In this paper, we introduce CityCompiler, an integrated environment for the iteration-based development of spatial interactive systems. CityCompiler visualizes interactive systems in a virtual 3D space by combining the Processing source code and the 3D model of the real space, designed with Google SketchUp. A simulation in virtual space enables us to test a spatial layout and a combination of components. In addition, the system function of smoothly switching between a virtual sensor and a real sensor realizes hybrid prototyping by means of virtual simulation and miniature simulation. These features integrate the space design with the software design and allow the smooth deployment of spatial interactive information systems into the real world.