The gently curving roof spans the full width of the site on the eastern, narrow, side and tapers towards the river. It also decreases in height in this direction. The result is a truncated cone. The railway line cuts through the seven bays of the membrane roof such that two bays span over the leisure facilities, five over the shopping zone. The roof structure is supported by 36m high steel columns which carry the trussed arches of steel circular hollow sections. Between these, further similar arches run in two diagonal directions.
On plan the roof is therefore a network of rhombuses and triangles which determine the shapes of the two-layer foil cushions by seele cover. The cushions are framed by aluminium sections on all sides which are fixed to steel channels. These are in turn raised 2m above the arch structure. The LED lighting to the roof – in all the colours of the rainbow – is a spectacular effect. The light from the LEDs mounted on the transverse axes is reflected by a pattern of white dots printed on the underside of the top layer of foil. In order to find the right pattern and colour for the dots, seele carried out large-scale lighting tests outdoors at its headquarters in Gersthofen. So now in the Confluence, the ”Fêtê des Lumières” can be celebrated every evening.