In 1218 Alfonso IX of Castile–León (reg 1188–1230) made the cathedral school an Estudio General and in 1253 it began to be called a university. The Universidad de Salamanca is one of the oldest in Europe and was favoured by all the kings of Castile and by the popes, especially Benedict XIII (reg 1394–1423) and Martin V. The latter approved its final constitution in 1442 and declared it a pontifical college. The Escuelas Mayores building was begun in 1415 and was extended between 1442 and 1452, the library (its vaults decorated c. 1479–83 by Fernando Gallego) and chapel (second half of the 15th century; decorated by Gallego and Juan de Borgeña) being built later. The sumptuous main façade, known as the fachada rica, was constructed (1510–20) in Renaissance style with iconographic allusions to Emperor Charles V.