Potsdam (.mw-parser-output .IPA-label-small{font-size:85%}.mw-parser-output .references .IPA-label-small,.mw-parser-output .infobox .IPA-label-small,.mw-parser-output .navbox .IPA-label-small{font-size:100%}German pronunciation: [ˈpotsdam] ⓘ) is the capital and largest city of the German state of Brandenburg. It is part of the Berlin/Brandenburg Metropolitan Region. Potsdam sits on the River Havel, a tributary of the Elbe, downstream of Berlin, and lies embedded in a hilly morainic landscape dotted with many lakes, around 20 of which are located within Potsdam's city limits. It lies some 25 kilometres (16 miles) southwest of Berlin's city centre. The name of the city and of many of its boroughs are of Slavic origin. Potsdam was a residence of the Prussian kings and the German Emperor until 1918. Its planning embodied ideas of the Age of Enlightenment: through a careful balance of architecture and landscape, Potsdam was intended as "a picturesque, pastoral dream" which would remind its residents of their relationship with nature and reason.[3] The city, which is over 1,000 years old, is widely known for its palaces, its lakes, and its overall historical and cultural significance. Landmarks include the parks and palaces of Sanssouci, Germany's largest World Heritage Site, as well as other palaces such as the Orangery Palace, the New Palace, Cecilienhof Palace, and Charlottenhof Palace. Potsdam was also the location of the significant Potsdam Conference in 1945, the conference where the three heads of government of the USSR, the US, and the UK decided on the division of Germany following its surrender, a conference which defined Germany's history for the following 45 years.