The Austrian architect and urban planner Siegfried Sitte (1876-1945) is the last representative of a family of architects spanning three generations, after Franz and Camillo Sitte. However, his extensive oeuvre, unlike that of his predecessors, is largely forgotten today. After sudden death of his father, great expectations were placed in Siegfried Sitte as successor of the well-known urban planning theorist Camillo Sitte. And Siegfried’s career began promisingly with contributions to international urban planning competitions. These designs, which were created up until the outbreak of World War I, represent Siegfried Sitte's early creative period. In fact, however, only a few of these projects were realised. For the first time, Siegfried Sitte’s largely unknown urban planning projects, which can be found in the estate of the Sitte family of architects, are made accessible to experts and analysed in detail. What are the qualities of Siegfried Sitte's urban designs? To what extent can the influence of Camillo Sitte's urban planning theories be detected in his son's work? Based on these central questions, it will be discussed whether Siegfried Sitte's urban planning has perhaps been unjustly neglected.