UNESCO Geopark, the first Geopark in North America, is centred around Saint John. The Geopark has been recognized by UNESCO as having exceptional geological significance. The park contains rock formations that date back to the Precambrian era and some of the rocks may be a billion years old. The Saint John River itself flows into the Bay of Fundy through a narrow gorge several hundred metres 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 create a series of rapids. The topography surrounding Saint John is hilly; a result of the influence of two coastal mountain ranges which run along the Bay of Fundy – the St. Croix Highlands and the Caledonia Highlands. The soil throughout the region is extremely rocky with frequent granite outcrops. The coastal plain hosts numerous freshwater lakes in the eastern, western and northern parts of the city. In Saint John the height difference from low to high tide is approximately 8 metres (28 ft) due to the funnelling effect of the Bay of Fundy as it narrows. The Reversing Falls in Saint John, actually an area of strong rapids, provides one example of the power of these tides; at every high tide, ocean water is pushed through a narrow gorge in the middle of the city and forces the Saint John River to reverse its flow for several hours. Neighbourhoods South (End) Central Peninsula—Uptown: on the east side of Saint John Harbour and the area immediately opposite on the west side are the sites of the original city. Now includes the central business district and the Trinity Royal Heritage Conservation Area, which together are referred to as Uptown. North End (Portland/Millidgeville): mostly the former city of Portland, formerly the site of ferry terminals. It is the site of the city's only completely French school and community centre, Centre Scolaire Communautaire Samuel-de-Champlain. It includes one of Canada's largest urban parks, Rockwood Park. East Side: east of the Courtney Bay contains commercial retail centres and residential subdivisions. West Side: west of the Saint John River is collectively referred to as West Side but Lancaster was a notable former municipality. Climate The climate of Saint John is humid continental (Köppen climate