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,
Kingdom of Sardinia Sardinia, including the city of Alghero and the semiautonomous Republic of Sassari, and added them to its direct domains. The Giudicato of Arborea, the only Sardinian state that remained independent of foreign domination, proved far more difficult to subdue. Threatened by the Aragonese claims of suzerainty and consolidation of the rest of the island, in 1353 Arborea, under the leadership of Marianus IV, started the conquest of the remaining Sardinian territories, which formed the Kingdom of Sardinia. In 1368 an Arborean offensive succeeded in nearly driving the Aragonese from the island, reducing the "Kingdom of Sardinia and Corsica" to just