The prisoners there built parts, sub-assemblies and BMW 003 turbojet engines for the He 162 jet fighter in a hastily-converted underground factory during late autumn and spring 1945.
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During World War II, a satellite camp of Mauthausen concentration camp was opened inside the caverns, producing parts for the He 162 jet fighter.
His mansion in Hinterbrühl became a meeting point for Jewish families and non-Jewish opponents of National Socialism, for example the pianists Erna Gál and Isa Strasser, as well as Ernst Wildgans, the Przibrams and Dr. Ella and Kurt Lingens.