influx. Construction of a new metro line connecting the part of the city north of the IJ to its southern part was started in 2003. The project was controversial because its cost had exceeded its budget by a factor of three by 2008, because of fears of damage to buildings in the centre, and because construction had to be halted and restarted multiple times. The new metro line was completed in 2018. Since 2014, renewed focus has been given to urban regeneration and renewal, especially in areas directly bordering the city centre, such as Frederik Hendrikbuurt. This urban renewal and expansion of the traditional centre of the city—with the construction on artificial islands of the new eastern IJburg neighbourhood—is part of the Structural Vision Amsterdam 2040 initiative. Geography Amsterdam is located in the Western Netherlands, in the province of North Holland, the capital of which is not Amsterdam, but rather Haarlem. The river Amstel ends in the city centre and connects to a large number of canals that eventually terminate in the IJ. Amsterdam is about below sea level. The surrounding land is flat as it is formed of large polders. An artificial forest, Amsterdamse Bos, is in the southwest. Amsterdam is connected to the North Sea through the long North Sea Canal. Amsterdam is intensely urbanised, as is the Amsterdam metropolitan area surrounding the city. Comprising of land, the city proper has 4,457 inhabitants per km2 and 2,275 houses per km2. Parks and nature reserves make up 12% of Amsterdam's land area. Water Amsterdam has more than of canals, most of which are navigable by boat. The city's three main canals are the Prinsengracht, Herengracht and Keizersgracht. In the Middle Ages, Amsterdam was surrounded by a moat, called the Singel, which now forms the innermost ring in the city, and gives the city centre a horseshoe shape. The city is also served by a seaport. It has been compared with Venice, due to its division into about 90 islands, which are linked by more than 1,200 bridges. Climate Amsterdam has an oceanic climate (Köppen: Cfb) strongly influenced by its proximity to the North Sea to the west, with prevailing westerly winds. Amsterdam, as well as most of the North Holland province, lies in USDA Hardiness zone 8b. Frosts mainly occur during spells of easterly or northeasterly winds from the inner European continent. Even then, because Amsterdam is surrounded on