The Island of Orleans is situated between the Laurentian Plateau or Canadian Shield to the north and the Appalachian Mountains to the south. Its north-eastern point marks the boundary between the St. Lawrence River and its estuary (the largest in the world), where fresh water begins to mix with salt water.
Of irregular form with jagged coves and capes, the Island of Orleans is 34 kilometres (21 mi) long and 8 kilometres (5.0 mi) wide at the widest point. It is 75 kilometres (47 mi) in circumference, with a total surface area of 190 square kilometres (73 sq mi). It has a hilly relief, small valleys, and gradual crests that reach a maximum height of about 150 metres (490 ft) at Sainte-Pétronille and Saint-Laurent in the south
