The World Cup 2006 brought with it the opportunity to convert the
legendary Wald Stadium into a large-scale arena for sports, concerts, business and other major events. Therefore a closed roof over the playing field was required, ideally a retractable roof construction. The world-wide biggest retractable roof was created, unfolding radially towards the center and disappearing inside the video-cube. The advanced development of the spoke-wheel principle made it possible to realize the design: above the grandstand a fixed roof was installed. It consists of an outer compression ring and two splayed inner tension rings, connected by 44 radial cables. The permanent roof structure concentrates the deviation forces at the corners, thereby adapting to the grandstand. The fixed roof is covered by a translucent membrane, which is replaced by a transparent polycarbonate skin in the front portion to ensure sufficient influx of daylight for the lawn.