The dissertation sheds light on the historical dimension of building relocations in urban planning. For the first time, relocation is examined as a method for urban reconstruction. From the detailed history of the concept and individual examples, the relocation of the Berlin courthouse arbor crystallizes as the ignition point of urban planning relocations. With the first urban planning publications, the model set a precedent. During various urban planning interventions and breakthroughs around 1900, material worthy of preservation was stored and reused. In cities with a corresponding building stock, the method became a system. Responsible for this were monument conservators, who could not yet be sharply separated from urban planners. Finally, relocation was used systematically on a large scale in the urban redevelopment of the 1930s and in the reconstruction of many large West German cities. Urban planning models make it clear that until the 1970s, relocations were seen as an equal response to urban development issues alongside adaptation new construction, square reconstruction, and arcade construction. Especially the area redevelopments from the 1960s onward offered space for reorganized urban areas in which original substance was supposed to bind urban identity as an anchor of historicity and authenticity. The individual buildings were often considered to be of little preservation value, but in a larger context they were perceived as having an impact on the cityscape. Only rarely was the work done true to the original according to today's understanding; rather, it was a matter of the ensemble effect of certain old town areas. In this way, old towns of typical shape were constituted, whose associated narrative does not reveal the history of their origin to uninformed observers - an omission that calls authenticity into question. Despite the dismissive attitude of many experts, many people today perceive the districts with relocated buildings as an immanent original part of their surroundings.In no other major German city was this done on such a massive scale as in Aachen. In the city area, there are at least 50 buildings whose facades consist of relocated elements, as well as at least 15 facade reconstructions and more than 25 other buildings constructed or supplemented with historic building materials. This was favored by the typical regional architecture of the bound brick building, whose architectural structuring elements are made of bluestone. The example is used to examine how the collection of old building components can become a system, how a workable consensus must be found between urban planning and monument value. Two time phases are to be distinguished: the actual reconstruction on destroyed building sites and the urban redevelopment in defined areas with extensive demolitions and new planning. Reconstruction depended heavily on the directing protagonists. The urban design of Aachen must be seen in the context of the city's history and structural factors. Accordingly, the reorganization planning has to be considered in the context of time. In order to reappraise the history of planning and the systematic handling of material, it was possible to access a vast number of previously unknown sources. The core of the dissertation is the description of the different types of relocations in the 20th century. Here it becomes clear how initial individual fragments and wartime destruction successively gave rise to a stockpiling and planned use of stored facades that had to give way to urban planning elsewhere. It goes without saying that this method, which was applied throughout Europe, required a massive critical debate in which prices and professional criticism stood irreconcilably in opposition to each other. Essential architectural aspects, such as the special nature of the corner, both the historical and the new interpretation of the transitions, or the deliberate staging and idealization of certain facades, illustrate the design aspirations of the architects in dealing with the old material. The urban design with old facades was part of an extremely modern urban redevelopment, which attempted to mitigate the structural change through visual effects. The new design of the old town also gives a modeled framework to the surroundings of the two central monuments of Aachen's urban history. In conclusion, therefore, it remains to be clarified how the monumental value of these buildings is defined today - after the end of this urban development phase.