Berlin is the capital city and one of the sixteen states of the Federal Republic of Germany. It is the heart of the Berlin-Brandenburg metropolitan region, located in northeastern Germany. With a population of 3.4 million in its city limits, Berlin is the country's largest city, and the second most populous city in the European Union. The Berlin metropolitan area is the fifth largest in the EU with a population of 4.9 million people from over 180 nations.**********************Berlin is located in eastern Germany, about 70 kilometres (44 mi) west of the border with Poland in an area with marshy terrain. Berlin's landscape was shaped by ice sheets during the last ice age. The city centre lies along the river Spree in the Berlin-Warsaw Urstromtal (ancient river valley), formed by water flowing from melting ice sheets at the end of the last Ice Age. The Urstromtal lies between the low Barnim plateau to the north, and the Teltow plateau to the south. In Spandau, Berlin's westernmost borough, the Spree meets the river Havel, which flows from north to south through western Berlin. The course of the Havel is more like a chain of lakes, the largest being the Tegeler See and Großer Wannsee. A series of lakes also feeds into the upper Spree, which flows through the Großer Müggelsee in eastern Berlin.*************Substantial parts of present-day Berlin extend onto the low plateaus on both sides of the Spree Valley. Large parts of the boroughs Reinickendorf and Pankow lie on the Barnim plateau, while most of the boroughs Charlottenburg-Wilmersdorf, Steglitz-Zehlendorf, Tempelhof-Schöneberg, and Neukölln lie on the Teltow plateau. The borough of Spandau lies partly within the Berlin Urstromtal and partly on the Nauen Plain, which stretches to the west of Berlin. The highest elevations in Berlin are the Teufelsberg in the borough of Charlottenburg-Wilmersdorf and the Müggelberge in the borough of Treptow-Köpenick. Both hills have an elevation of about 115 metres (377 ft). The Teufelsberg is in fact an artificial pile of rubble from the ruins of World War II.*********************The city's appearance today is predominantly shaped by the key role it played in Germany's history in the 20th century. Each of the national governments based in Berlin—the 1871 German Empire, the Weimar Republic, Nazi Germany, East Germany, and now the reunified Germany—initiated ambitious construction programs, each with its own distinctive character. Berlin was devastated by bombing raids during World War II and many of the old buildings that escaped the bombs were eradicated in the 1950s and 1960s in both West and East. Much of this destruction was initiated by municipal architecture programs to build new residential or business quarters and main roads. Berlin's unique recent history has left the city with an eclectic array of architecture and sights. In the eastern part, many Plattenbauten can be found, reminders of Eastern Bloc ambitions to create complete residential areas with fixed ratios of shops, kindergartens and schools. Another difference between former east and west is in the design of little red and green men on pedestrian crossing lights (Ampelmännchen in German); the eastern versions received an opt-out during the standardization of road traffic signs after reunification. The eastern Ampelmännchen design is now used in the western part of the city as well.********************Berlin is subdivided into twelve boroughs (Bezirke), but before Berlin's 2001 administrative reform there were 23. Each borough is subdivided into a number of localities (Ortsteile), which represent the traditional urbanized areas that inhabitants identify with. Some of these have been rearranged several times over the years. At present the city of Berlin consists of 95 such localities. The localities often consist of a number of city neighbourhoods (usually called Kiez in the Berlin dialect) representing small residential areas. Each borough is governed by a borough council (Bezirksamt) consisting of five councilors (Bezirksstadträte) and a borough mayor (Bezirksbürgermeister). The borough council is elected by the borough assembly (Bezirksverordnetenversammlung). The boroughs of Berlin are not independent municipalities. The power of borough governments is limited and subordinate to the Senate of Berlin. The borough mayors form the Council of Mayors (Rat der Bürgermeister), led by the city's Governing Mayor, which advises the Senate. The localities have no government bodies of their own, even though most of the localities have historic roots in older municipalities that predate the formation of Greater Berlin on 1 October 1920. The subsequent position of locality representative (Ortsvorsteher) was discontinued in favour of borough mayors.