This book offers a groundbreaking perspective on Judeo-Christian coexistence in medieval Spain, in particular on the Camino de Santiago (Way of St. James), one of the most important pilgrimage routes in Europe. The author uncovers new evidence of Judeo-Christian cooperation in Castilian monasteries on the Camino. It reveals that a collaborative climate endured in these monasteries as demonstrated by the transmission of cuaderna vía poetry from Christians to Jews. The research focuses on poems written by Jews in Castilian (Spanish) during the thirteenth and fourteenth centuries that illustrate a progressive mastery of cuaderna vía poetry, which is the product of interaction in monastic schools between Jews and Christian clerics who created and cultivated this Castilian poetic form.