Katerina Beranova (L) and Alexandra Diesterhoeft (R) perform during the premiere of the opera “Spiegelgrund." Spiegelgrund was the name of a clinic for socially deprived children. These “anti-social” or “problem” children failed to measure up to the norm in Vienna during the Nazi dictatorship and were collected for extermination without their parents’ or caretakers’ knowledge or consent. (DIETER NAGL/AFP/Getty Images