Aunis () is a historical province of France, situated in the north-west of the department of Charente-Maritime. Its historic capital is La Rochelle, which took over from Castrum Allionis (Châtelaillon) the historic capital which gives its name to the province. It was a fief of the Duchy of Aquitaine. It extended to Marais Poitevin in the north, Basse Saintonge (and Niortais) in the east, and Rochefortais in the south. Aunis had an influence approximately 20–25 km into the Isle of Ré (l'Île de Ré). The province was officially recognised during the reign of Charles V of France in 1374: "In 1374, Charles V separated La Rochelle from Saintonge to set up a provincial government, comprising the jurisdictions of Rochefort, Marennes and, for a time, Benon. It was thus that Aunis legally became a separate province." Aunis was the smallest province in France, in terms of area. Nowadays it is a part of the Charente-Maritime département together with Saintonge. People from Aunis were called Aunisien (masculine) or Aunisienne (feminine). The English term is Aunisian. Geography Aunis is mostly a rolling chalk plain, whose navigable rivers have always been important modes of communication, and from which came economic development and the urbanisation of the region. The region is coastal, with varied seafronts and offshore islands, from which maritime activities diversified. Nowadays tourism is of great importance. Geographic framework Aunis has two river borders, those of the Sèvre Niortaise in the north, and the Charente in the south. To the west is the Atlantic Ocean and two islands, the Île de Ré and the Île d'Aix. To the east it is bordered by the valley of the Mignon (the main left tributary of the Sèvre Niortaise), by the hills of Saintonge around Saint-Félix, and by the valleys of the Trézence and Boutonne. Aunis is a chalk plain of the Jurassic period, characterised by gently rolling hills, where no valley is completely enclosed, and where the land has a regular descent towards the sea. The islands of Ré and Aix were made at the same time and from the same type of rock. The chalk table completes the triangular promontory which juts into the Atlantic, forming the northern extremity of the Aquitaine Basin. Large freshwater and seawater marshes have formed in places that have been drained, hardly altering the general relief. The seawater marshes correspond to ancient marine gulfs, made from marine or fluvial