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‘Plan F’ is one of seven remaining medieval architectural sketches of Cologne Cathedral. The plan, which shows the western façade of the cathedral, stands out from other sketches dating from the close of the thirteenth century in terms of its size (4.05 metres) and the accuracy of the drawing. The elevation is made up of 20 sheets of parchment that have been stuck together. For many years, the plan was considered lost. It was discovered in two halves: the plan of the north tower was found in the attic of the guest house ‘Zur Traube’ in Darmstadt in 1814, and the plan of the middle section and south tower was discovered in an antique shop in Paris two years later. This rediscovery proved vitally important for the completion of the cathedral in the nineteenth century.