97. 1908. Prague. Mahler with conductor Bruno Walter (1876-1962) (right). These photographs are believed to have been taken around 09-1908 when Mahler was here to conduct the world premiere of his Symphony No. 7. Earlier, in 01-1908, Mahler had made his deput with the New York Metropolitan Opera (MET) (Tristan und Isolde) to great acclaim.