zero), A is the number of the post office (irrelevant in this case, usually zero). Example: 1070 for Neubau. Exceptions of that are 1300 for the Vienna International Airport located in Lower Austria near Schwechat, 1400 for the UN Complex, 1450 for the Austria Center Vienna, and 1500 for the Austrian UN-Forces. The numbering of the districts reflects to some degree when they were incorporated into Vienna. The first district comprises not much more than Vienna's historic centre, which used to be the entire city until 1850. Districts 2–9 (and 20 which was in 1900 separated from the second district), incorporated in 1850, are known as Innenbezirke (inner districts) and composed of the former Vorstädte, which were located inside the Linienwall, the second ring of fortifications around Vienna. Those districts are located within the Gürtel today. The other districts, incorporated between 1874 and 1938, mainly in 1892, are known as Außenbezirke (outer districts) and are the former Vororte. District populations The following are current district populations, as of 2016-01-01 (source): See also For the creation and administration of the districts, see . Arrondissements of Paris History of Vienna List of urban areas in the European Union References External links Districts of Vienna Interactive Map