In the period 2010-2013 Guy Cassiers directed the opera cycle Der Ring des Nibelungen by Richard Wagner. The musical direction was in the hands of the world-renowned conductor Daniel Barenboim. Der Ring des Nibelungen was a production of Teatro alla Scala and the Staatsoper Unter den Linden in Berlin, in cooperation with Toneelhuis.
Kurt d’Haeseleer created together with Arjen Klerkx the videodesign for Rheingold, the first opera of the cycle.