Countess Urraca Lope de Haro was the daughter of the noble Lord Diego Lope de Haro, friend and advisor to King Alfonso VIII of Castilla-León and granddaughter of Lord Lope Díaz de Haro and Lady Aldonza Ruiz de Castro, aristocratic courtiers as well as popular monastic patrons. As a young and wealthy widow, Countess Urraca took monastic vows at the Cistercian nunnery of Santa María de Cañas founded by her grandparents. Within a short time of uniting herself to this monastery, she was chosen as its fourth abbess in 1225, a position she held for thirty-seven years until her death in 1262. Following the tradition of monastic patronage established by her noble family members, Countess Urraca expanded the monastery's small real estate holdings, oversaw extensive building projects to create permanent structures for the nunnery, and patronized artistic projects including statuettes of the Virgin Mary and St. Peter in addition to her own decorative stone sarcophagus during her term as abbess. This thesis examines the artistic decoration and architectural patronage of this powerful woman and the influences she incorporated into the monastic structures at Cañas as she oversaw their construction. In dating the original buildings of the monastery at Cañas to the period of Countess Urraca's leadership, the predominant architectural features and decorative details of female Cistercian foundations in northern Spain are discussed. Comparisons with additional thirteenth-century Cistercian monasteries from the same region in northern Spain are offered to demonstrate the artistic connections with the structures Countess Urraca patronized. In addition, this thesis examines Countess Urraca's obvious devotion to the Virgin Mary and St. Peter by considering the medieval monastic world in which she lived and the strong emphasis the Cistercian Order placed on such worship practices. The potent spiritual connections Countess Urraca made by commissioning images of essential, holy intercessors testifies to her devotion to them and the powerful salvatory role she herself played in the lives of the nuns for whom she was responsible. As a nun and abbess, Countess Urraca was urged to emulate Mary's mothering, nurturing qualities, and, as she did so was simultaneously empowered by the Virgin's heavenly authority as administrator of mercy. Indeed, through studying her art it is clear that she saw herself as an intercessor on behalf of the nuns for whom she was responsible. Furthermore, discussion of the imagery displayed on Countess Urraca's decorative stone sarcophagus demonstrates not only a similar message of salvation through intercessors such as Peter and Mary, but also testifies of Abbess Urraca's aristocratic lineage. Through this artistic commission, the Abbess creates another direct, personal link between herself and the Virgin by including the symbol of the rosary throughout the iconography of her tomb. Such a symbol represents her devotion to Mary as Queen of Heaven and simultaneously empowers Countess Urraca as an intercessor herself. All of these architectural and artistic commissions confirm that she was a powerful woman who wielded a great deal of influence.