International Medieval Society, Paris
Société Internationale des Médiévistes, Paris

Symposium 2009 - Space/l'Espace
Abstract

Today it is commonly accepted that medieval architecture was based on ‘Ad quadratum’ geometry. In the past fifty years, scholarship has stressed its practical advantages over its identity as a consequence of religious symbolism. By discovering its use in urban planning, recent research has revealed a wider range of applications, and yet we are still left with a pretty coarse picture. Like “international gothic” for painting, 'ad quadratum' geometry is a phrase employed in conjunction with a large number of artistic phenomena. Now that we are convinced of its relevancy, I think it is time to detail its diffusion routes and the various forms it took. To undertake such a task, I would like to focus on eleventh-century Lombardy, which, as my research highlights, was a diffusion centre for ‘Ad quadratum’ geometry.
Before moving to Rheims (usually acknowledged as the cradle for the revival of Ad quadratum’ geometry), Gerbert d¹Aurillac was abbot of Bobbio Abbey, where he may have read the Corpus Agrimensores Romanorum. Many neighboring cities, from Cremona to Modena, abound with rigorous examples of geometric planning. Further, Pisa cathedral, of whose plan I present a new possible rationale, was built after summoning Lombard architects. Although Lombard architecture never achieved the sophistication of northern French architecture, its reliance on ‘Ad quadratum’ principles offers an interesting case to start a more accurate map of the transmission of this important architectural practice.