Conductor Daniel Barenboim has courted Wagner-related controversy in the past, challenging Israel’s unofficial ban on the notoriously anti-Semitic composer’s music. Now, he’s bringing his Divan Orchestra, made up of Palestinian and Israeli musicians, to Berlin, to perform Wagner’s Die Walküre at Waldbuhne, the outdoor arena built for the Berlin Olympics in 1936 at which some athletes gave the Nazi salute in front of Hitler.