There are two river estuaries on the north coast: Hayle Estuary and the estuary of the River Camel, which provides Padstow and Rock with a safe harbour.
The north coast on the Celtic Sea, part of the Atlantic Ocean, is more exposed and therefore has a wilder nature.
The coastline is composed mainly of resistant rocks that give rise in many places to tall cliffs.
Cornwall has a border with only one other county, Devon, which is formed almost entirely by the River Tamar, and the remainder (to the north) by the Marsland Valley.
Extensive stretches of Cornwall's coastline, and Bodmin Moor, are protected as an Area of Outstanding Natural Beauty. It is regarded as the county flag by Cornwall Council.
The banner of Saint Piran is a white cross on a black background (in terms of heraldry 'sable, a cross argent').