differs from that on the slopes and in the higher areas, where the Dresden district Klotzsche, at 227 metres above sea level, hosts the Dresden weather station. The weather in Klotzsche is colder than in the inner city at 112 metres above sea level. Flood protection Because of its location on the banks of the Elbe, into which some water sources from the Ore Mountains flow, flood protection is important. Large areas are kept free of buildings to provide a flood plain. Two additional trenches, about 50 metres wide, have been built to keep the inner city free of water from the Elbe, by dissipating the water downstream through the inner city's gorge portion. Flood regulation systems like detention basins and water reservoirs are almost all outside the city area. The Weißeritz, normally a rather small river, suddenly ran directly into the main station of Dresden during the 2002 European floods. This was largely because the river returned to its former route; it had been diverted so that a railway could run along the river bed. Many locations and areas need to be protected by walls and sheet pilings during floods. A number of districts become waterlogged if the Elbe overflows across some of its former floodplains. City structuring Dresden is a spacious city. Its boroughs differ in their structure and appearance. Many parts still contain an old village core, while some quarters are almost completely preserved as rural settings. Other characteristic kinds of urban areas are the historic outskirts of the city, and the former suburbs with scattered housing. During the German Democratic Republic, many apartment blocks were built. The original parts of the city are almost all in the boroughs of Altstadt (Old town) and Neustadt (New town). Growing outside the city walls, the historic outskirts were built in the 18th and 19th century. They were planned and constructed on the orders of the Saxon monarchs and many of them are named after Saxon sovereigns (e.g. Friedrichstadt and Albertstadt). Dresden has been divided into ten boroughs called "Stadtbezirk" and nine former municipalities ("Ortschaften") which have been incorporated since 1990. Demographics The population of Dresden grew to 100,000 inhabitants in 1852, making it one of the first German cities after Hamburg, Berlin and Breslau to reach that number. The population peaked at 649,252 in 1933, and dropped to 368,519 in 1945 because of World War II, during which large