This publication documents a little-known temporary artwork. In the winter of 1973/74, Paul Thek (1933–1988) was a guest of the Lehmbruck Museum in Duisburg, where he installed the room-filling environment "Ark, Pyramid – Christmas" ("The Manger")—a development of the legendary "Pyramid" installation realized at Documenta 5 in 1972. This exhibition, organized by the director of the museum at the time, Siegfried Salzmann, was the fourth in Thek’s large-scale projects in Europe, all of which engaged with individualized religious symbols (or what Harald Szeemann termed "Individual Mythologies"). The Christmas season provided Thek with the occasion to present, for the first time, a self-written theater piece in the form of a nativity play featuring children from Duisburg. This book reproduces the museum’s archival materials, offering a reconstruction of the exhibition. It includes an interview with Edwin Klein, who assisted with Thek’s installation.