The retable of Pedro de Montoya, bishop of Osma (1453–1474), is the largest example of an embroidered altarpiece. It is a telling object, when it comes to describing the artistic transfer between Northern Europe and Iberian Peninsula as well as cross media connections in a textile technique pointing to painting, to sculpture and architectural elements. Today, the retable is part of the collection of the Art Institute of Chicago. In anticipation of the opening of its new medieval galleries in 2017, the altarpiece underwent conservation / restoration and technical documentation in the Abegg-Stiftung in Riggisberg. This was followed by an international workshop focusing on the concept and technique of the altarpiece as well as on its art historical and historical context. The essays published here locate this masterpiece of an ambitious donor in the artistic milieu of fifteenth-century Castile. Contributions on the art of embroidery in the Crown of Aragon complete the volume.