Altars within large churches were set apart in some way.  An elevation consisting of a reliquary shrine under a metal or stone canopy was a frequent choice for builders.  A series of tall pedestals with statues of angels carrying signs of the Passion flanked this altar.  Between the columns, cloth hangings separated the place of performance from the space of passage within the cathedral.  Fabrics were some of the most valued objects of the Middle Ages, and often richly embroidered materials acted as screens for the sacrament. (Viollet-le-Duc, Architecture, 2:29: Arras Cathedral) back to "worship"