 These plans were given the lengthy title of "La Collaboration Internationale entre Artistes et Architectes dans la realization du Nouvel Opéra et theater de Gelsenkirchen" ("International Collaboration between Artists and Architects in the realization of the New Opera and theater of Gelsenkirchen"), and acted as a sort of avant-garde press release for the new opera house.In June 1959, the Iris Clert Gallery held what was to be Klein's final exhibition in the gallery, "La forêt d'ésponges monochromes" ("Forest of Monochrome Sponges").The exhibition displayed a new tangent of Klein's