Walls, windows, doors and satellite dishes tessellate at twilight into a patchwork pattern in the madinah, or walled old city, of Fez, Morocco, as a pedestrian passes into view along one of the city’s typically narrow stone streets. Nestled in a valley crowned by gentle hills, Fez is one of the Islamic world’s great historic centers of the art of geometrically based patterns executed in tile, plaster, stone, wood and metal. Like all such patterns, those that adorn the mosques, madrassahs (schools) and sabeels (fountains) of Fez have their origins in simple, universal geometry that— through practice and elaboration—artists and craft workers developed into celestially intricate masterpieces. These adorn Fez in such numbers that the entire madinah is a UNESCO World Heritage Site. In May AramcoWorld editor Richard Doughty joined a workshop to learn firsthand from the city’s great works, starting with a straightedge, a compass, a pencil and paper. (And an eraser.)