This contribution was produced to the Documenta 5 in Kassel: a transparent sphere with a diameter of 8 metres was placed in front of the main facade of the Friedericianum. A catwalk made of standard tubular steel sections projected through a window from the interior of the building. A tubular steel ring was fixed to this footbridge, at a slight distance from the façade. This ring formed the external support for a PVC foil shell that formed a sphere when inflated into shape by an air pump.