With relatively small modifications, the Liber Augustalis remained the basis of Sicilian law until 1819. His royal court in Palermo, from around 1220 to his death, saw the first use of a literary form of an Italo-Romance language, Sicilian, that had a significant influence on what was to become the modern Italian language. During this period, he also built the Castel del Monte, and in 1224, he founded the University of Naples, now called, after him, Università Federico II.[20]