This ecclesiastical museum's collection is of considerable historical and artistic significance. Among its treasures are the reliquary of St Isidore (11C), a wood casket covered in hammered gold and silverwork; the Doña Urraca chalice composed of two Romano-Oriental onyx cups; and a 12C enamel casket incorporating 17 leather panels decorted with Limoges enamelwork. The library has 800 parchments, 400 incunabula including a Mozarabic bible (960), and 1 055 rare and ancient books (16C-18C).