The building of the Österreichische Postsparkasse (Austrian postal savings bank) in Vienna was built by Otto Wagner from 1904-06. It was an architectural highlight of the Viennese Secession: ferro-concrete ceilings, modifiable, non-structural walls. Light-flooded working environment. The façade, with marble cladding hanging on aluminium nails, was an innovation. It was the first time that facades had been clad in this way. The visible aluminium bolts also fulfilled the aesthetic intent of giving the impression of a bank vault.