The aim of this document is to provide an overview of the design of the OpenGEM system, within the scope of the GEM1 project. OpenGEM is the name that was chosen for the IT platform which will allow calculation and communication of earthquake risk on a global scale. One of the goals of the GEM1 project was to design an initial model building structure and this report hence describes the various components of the design. The IT infrastructure described in this report has been reviewed during an intensive IT-review after which a strategy has been determined for further development of GEMs IT architecture, which makes use of the work done during GEM1, but has taken a different approach.