The Austrian Post Office Savings Bank

Wagner's Post Office Bank was won in competition in 1903 and erected in two stages, 1904-06 and 1910-12. The Hall roof, completed as part of the first stage in 1906, was a major innovation although only a small part of the vast project. It covered the centrally positioned public space in the trapezoidal-shaped, six-storey building. The glazed vault was suspended from cables in the original competition design and a larger area was involved, but in the final design, a secondary roof was incorporated above the curved ceiling. The floor to the Hall was also finished in glass to allow light to penetrate rooms below."
Dennis Sharp: Twentieth Century Architecture: a Visual History, p.26-27