Vienna has more than its fair share of magnificent, beautiful and historically significant buildings. The Hofburg Palace, the Belvedere, Stephansdom, Schloss Schönbrunn, the Secession Building, Staatstoper, Karlskiirche, Hunderstwasshauss, Maolika Haus.

Along Helinganstädter Strasse, at the end of the U4 U-Bahn, stands a building that even its greatest admirers would not describe as magnificent or beautiful. It is, however, historically significant – though of a history that is often forgotten – and architecturally striking. The Karl Marx Hof, built between 1927 and 1930, is perhaps the greatest architectural monument to the days of ‘Red Vienna’ – the days when the city of Vienna was a major site of working class struggle. Sometimes described as the largest council block in Europe, Karl Marx Hof, which can sometimes look like a barricade from the outside, was a battlefield during the short-lived Austrian civil war of 1934, shelled by the army, attacked by right-wing paramilitaries, defended by its inhabitants. For both sides the building was not simply the home to thousands of working class radicals, but also symbolic of the struggle for a new Austria.

In the wake of the First World War, Austria was beset, as were many central European nations, with mass unemployment, and shocking levels of poverty and hunger. Most working class apartments in Vienna had no toilet or running water and lacked gas or electric lighting. So the city council, In the 1920s and 30s, dominated by Social Democrats who were well to the left of social democrats elsewhere, embarked on a major project of house building and urban renewal. Sixty-four thousand flats, housing a quarter of a million people, were built in the ten year period from 1923 to 1933. The legacy can still be felt – even today more than half the population of Vienna live in subsidized public housing.

Designed by Karl Ehn – not, as it happens, ever a socialist, but an architect who was later to collaborate on Nazi projects – the Karl Marx Hof is monumental. The building is more than a kilometer-long, modernist, enlivened by flashes of art deco-ish touches, with archways, statues murals, and turrets. Where previously, public housing projects had only communal toilets and cold water taps, every apartment in Karl Marx Hof had a toilet and cold running water, and there were balconies, until then considered an aristocratic luxury that no building designed to house the working class needed. It contained schools, nurseries, washhouses, a library and a medical centre – all of which still remain. And at the centre of every block were mini-parks, dotted with playgrounds – a revolutionary shift at a time when city flats generally opened out, if at all, into dingy airless yards, onto which other flats backed.

The days of Red Vienna are long gone. The large poster on the bus stop opposite Karl Marx Hof for Norbert Hofer, the candidate for the far-right FPO, sums up the change. Today, Karl Marx Hof can seem a bit rundown, old-fashioned, even mundane. Yet, as a symbol both of a significant moment not just in Austrian but in European history, and also of how it is possible to think of, and plan for, public housing, the Karl Marx Hof remains highly significant.