Saint John is a seaport city, located on the Bay of Fundy in the province of New Brunswick, Canada. It is the oldest incorporated city in Canada, established by royal charter on May 18 1785. Situated along the north shore of the Bay of Fundy at the mouth of the Saint John River, the city is split by the south-flowing river. Saint John Harbour is a deep water port which is ice-free all year round. The Saint John River itself flows into the Bay of Fundy through a narrow gorge several hundred feet wide at the centre of the city. It contains a unique phenomenon called the Reversing Falls where the diurnal tides of the bay reverse the water flow of the river for several kilometres. A series of underwater ledges at the narrowest point of this gorge also creates a series of rapids.