Kingdom of Sardinia and Aosta, dynastic possessions since the 11th century, the Principality of Piedmont (a possession built up in the 13th century), and the County of Nice (a possession since 1388). While in theory the traditional capital of the island of Sardinia and seat of its viceroys was Cagliari, the Piedmontese city of Turin was the "de facto" capital of Savoy. When the mainland domains of the House of Savoy were occupied and eventually annexed by Napoleonic France, the king of Sardinia made his permanent residence on the island for the first time in its history. The Congress of Vienna (1814–15), which
Sardinia mainland peninsula. The Strait of Bonifacio is directly north of Sardinia and separates Sardinia from the French island of Corsica. The coasts of Sardinia [ long] are generally high and rocky, with long, relatively straight stretches of coastline, many outstanding headlands, a few wide, deep bays, rias, many inlets and with various smaller islands off the coast. The island has an ancient geoformation and, unlike Sicily and mainland Italy, is not earthquake-prone. Its rocks date in fact from the Palaeozoic Era (up to 500 million years old). Due to long erosion processes, the island's highlands, formed of granite, schist, trachyte,