Aberdeen Harbour is a world class port annually handling around 5 million tonnes of cargo, valued at approximately £1.5 billion, for a wide range of industries. Aberdeen, often called The Granite City or The Silver City, is Scotland's third largest city, with a population of approximately 202,370. Aberdeen is the chief commercial centre and seaport in the north-east of Scotland. The city is often referred to as the Oil Capital of Europe thanks to becoming a major service base for the extraction of crude oil in the North Sea in the 1970s. The city forms the Aberdeen City unitary council area, and it is surrounded by the Aberdeenshire council area. It mostly stands between the mouths of the rivers Don and Dee. The harbour has direct links with around 30 countries, principally in Europe, West Africa, and North America while trans-shipment at Continental ports provides connections with other countries, as do ad hoc shipments.