Sardinia world (22 centenarians/100,000 inhabitants). Sardinia is the first discovered Blue Zone, a demographic and/or geographic area in the world with an oversize concentration of centenarians and supercentenarians. In 2016 there were 50,346 foreign national residents, forming 3% of the total Sardinian population. The most represented nationalities were: Sardinia's most populated cities are Cagliari and Sassari. The Metropolitan City of Cagliari has 431,302 inhabitants, or about ¼ of the population of the entire island. Eurostat has identified in Sardinia two Functional Urban Areas: Cagliari, with 477,000 inhabitants, and Sassari, with 222,000 inhabitants. Sardinia is one of the five Italian autonomous regions,
Sardinia Sardinia. Thus Sardinia is probably the only European country where feudalism was introduced in the transition period from the Middle Ages to the early modern period, at a time when feudalism had already been abandoned by many other European countries. In 1469, the heir to Sardinia, Ferdinand II of Aragon, married Isabel of Castile, and the "Kingdom of Sardinia" (which was separated from Corsica) was to be inherited by their Habsburg grandson, Charles I of Spain, with the state symbol of the Four Moors. The successors of Charles I of Spain, in order to defend their Mediterranean territories from raids