Which housing complex in Vienna is one of the world's longest residential buildings?

Karl-Marx-Hof is a Vienna housing complex widely known as one of the world’s longest residential buildings.

The complex was designed by architect Karl Ehn and built between 1927 and 1930 during Vienna’s major municipal housing program. It stretches for more than a kilometre along Heiligenstädter Straße, although its form is a sequence of connected wings rather than one uninterrupted block. The development was named Karl-Marx-Hof in 1949; it had previously carried another official name.

Its architecture combines housing with shared facilities, courtyards, towers, arches, and community services. The project reflected “Red Vienna,” a period when the city government invested heavily in publicly owned housing and urban infrastructure during the interwar years.

Karl-Marx-Hof is sometimes mistaken for a palace because of its monumental arches and towers. It is fundamentally a large municipal residential development, designed for working-class households rather than as a royal residence.