Capitolare library is housed in the palace of the Canonicato. Established as a "scriptorium" in the fifth century, it is one of the most important ecclesiastical libraries in Europe. Ancient books with miniatures, precious manuscripts and many rare publications are preserved there. Highlights: the Istituzioni di Gaio, the only extant text of Roman law almost complete, an edition of the De Civitate Dei of St. Augustine, probably contemporary to the author; Purple Book of the Gospels of the fifth century;  the Lettere d'Oro e d'Argento on purple parchment; numerous manuscripts of the ninth century and the collection of manuscripts collected by Scipione Maffei.