Two superposed Gothic churches make up Santander’s cathedral. In the lower, older, 13th-century Iglesia del SantÃsimo Cristo, glass floors reveal excavated remains of Roman Santander. Displayed nearby are silver vessels containing the skulls of the early Christian martyrs San Emeterio and San Celedonio, Santander’s patron saints. The care of these holy relics, found on this site in 1533, prompted the construction of the monastery that originally stood here.