The paper describes a space description language able to model domotic environments, including architectural elements, furniture and appliances. Objects are modeled defining their location, dimension and relative position in a high level language that hides all the annoying details needed to represent the environment in a 3d virtual world. The presented language (STEDEL) in particular allows to define rooms (only rectangular, although this restriction is likely to be removed in future extensions), furniture and appliances and to position them either by specifying the distance from walls and from the floor or by relative positioning, e.g. a lamp is over a table. A case study on domotic environments is described and a STEDEL compiler is available, which can created fully usable X3D models from a STEDEL specification. Scripting in X3D allows generated models to actually interact with real world domotic environments, thus providing means to design immersive simulation applications, interactive frameworks for teaching domotics, etc.