King Alfonso X’s scholarly activity is characterized by the use of the vernacular, the commissioning of works of encyclopedic scope, the mining of a wide variety of sources and collaborative authorship. Each of these features is apparent in his most famous sacred book, the Cantigas de Maria, the largest surviving medieval collection of the Virgin’s miracles. This paper will consider the Cantigas in the context of other works produced at Alfonso’s court in the second half of the thirteenth century, charting how the work grew from a modest selection of 100 miracles without illustrations into a pair of massive picture books with more than 2,800 individual scenes and every miracle set to music. I will suggest that secular and sacred were blurred in the context of the Spanish court and that similar approaches to the production of texts were sometimes adopted, regardless of subject matter.