Germany is located in central Europe, bordered to the north by Denmark and the North and Baltic Seas, to the east by the Czech Republic and Poland, to the south by Switzerland and Austria, and to the west by Belgium, Luxembourg, France and the Netherlands. Germay's borders contain a portion of the Alps mountains, the Black Forest, and the famous Rhine and Danube rivers.
Germany was unified as a nation in 1871, when the German Empire, dominated by the Kingdom of Prussia, was created. This began the German Reich. The word Reich is usually translated as "empire", but also means "kingdom", "domain" or "realm".
The Germanic tribes are thought to have formed during the Pre-Roman Iron Age in southern Scandinavia and northern Germany. From the first century BC these tribes began expanding south, east and west. Under Augustus, the Romans attempted to invade Germany, and from this period on the German tribes learned Roman tactics of warfare whilst maintaining their own distinct national identity. In AD 9 three Roman legions were defeated in the Battle of the Teutoburg Forest. Germany as far as the Rhine and the Danube consequently remained outside the Roman Empire. By AD 100, the Germanic tribes had settled along the Rhine and the Danube (the Limes Germanicus) and occupied most of the area of modern Germany. From 200 AD, a number of large West Germanic tribes (Alamanni, Franks, Chatti, Saxons, Frisians, Thuringians) began to emerge. Around 260, these Germanic peoples finally broke through the Limes and the Danube frontier. Subsequent migrations, motivated by the invasions of the Huns, population pressures, and climatic changes, included the Goths, Vandals, and Franks. Several Germanic peoples, including the Franks and Burgundians, invaded the Roman Empire and formed their own kingdoms.
Germany comprises sixteen states, which are subdivided into 439 districts and cities. The five largest cities in Germany are the capital Berlin (population 3.4 million), Hamburg (population 1.8 million), Munich (population 1.4 million), Cologne (population 980,000) and Frankfurt (population 660,000). The five largest metropolitan areas in Germany are Rhein-Ruhr (11.8 million inhabitants), Frankfurt Rhein-Main (5.8 million inhabitants), Berlin (4.3 million inhabitants), Hamburg (3.3 million inhabitants) and Stuttgart (2.4 million inhabitants).
Since reunification Germany has resumed its role as a major European crossroad between the Scandinavian north and the Mediterranean region south, and the Atlantic west and Slavic and Baltic east. Due to its central location, Germany shares borders with more European countries than any other country.
Germany's territory extends from the high mountains of the Alps (highest peak 2,962 metres) in the south to the shores of the North and Baltic Seas in the north. In between are the central German forests and the lowlands of northern Germany (lowest point 3.54 metres below sea level). Germany is traversed by several major European rivers including the Rhine, Danube and Elbe.
For the most part, Germany has a cool/temperate climate influenced by humid westerly winds and the Gulf Stream, which promotes a mild climate. To the north the climate is oceanic with rainfall all year round. Winters are mild and summers relatively cool, with temperatures occasionally rising above 30 degrees Celsius. To the east, Germany's climate is distinctly continental with cold winters, warm summers, and long dry periods often recorded. The centre and south of Germany has a transitional climate which ranges from moderately oceanic to continental depending on location. Warm summers with temperatures about 30 degrees Celsius (86 °F) are common.