In this talk Robert Bork will consider Gothic architectural drawings as vehicles for the transmission of geometrical information, placing their development in the context of a broader tradition of geometrical design that reaches with a surprising degree of continuity across the long Middle Ages. After brief discussion of the geometrical toolkit used by the creators of early medieval manuscripts and jewelry, he will explore the flourishing of architectural drawing in the Gothic era and its impact on both design practice and the sharing of visual information across temporal and geographical boundaries. He will devote particular attention to the analysis of a fantastic drawing produced in or near Regensburg around 1400 that shows a single-spired façade, whose close geometrical relationship to the thirteenth-century choir of Regensburg Cathedral has not formerly been recognized. In conclusion, he will demonstrate that many of the same geometrical techniques used by Gothic church designers were also used not only by some northern fifteenth-century painters, but also by Italian painters active in the decades around 1500, including Piero di Cosimo and Piero della Francesca.