This is the Vienna the twentieth century built. Between the wars, the socialist city government — Red Vienna — put up enormous, dignified housing blocks for working families, and the Karl-Marx-Hof is the one everyone means. Step off the U4 and it's across the road: a kilometre of ochre and red, four vast arches over the front, a statement you read before you've crossed the street.
Karl Ehn designed it, 1927 to 1930, more than a thousand flats around courtyards meant to give working families the light and air the old tenements never had. Stand under the central arch first, then walk through to the courtyards behind, where the idea becomes a place — gardens, not corridors. People live here; tread lightly.
From there it's a short pass through the Heiligenstädter Park and up the slope to the Hohe Warte, where Josef Hoffmann built villas around 1900 for artists and patrons — the private, Secession-era Vienna set against the Hof's collective one. Two ideas of how to live, ten minutes apart. Drop back down to the Donaukanal and follow the water south to the U4.
