Oder in the context of "Natural border"

Silesia (see names below) is a historical region of Central Europe that lies mostly within Poland, with small parts in the Czech Republic and Germany. Its area is approximately 40,000 km (15,400 sq mi), and the population is estimated at 8,000,000. Silesia is split into two main subregions, Lower Silesia in the west and Upper Silesia in the east.

Situated along the Oder River, with the Sudeten Mountains extending across the southern border, Silesia is a heavily industrialised region rich in mineral and natural resources. The largest city and Lower Silesia's capital is Wrocław; the historic capital of Upper Silesia is Opole. The biggest metropolitan area is the Katowice metropolitan area, the centre of which is Katowice. Parts of the Czech city of Ostrava and the German city of Görlitz are situated within Silesia's borders.

Ostrava (Czech pronunciation: [ˈostrava] ; Polish: Ostrawa; Silesian: Ôstrawa; German: Ostrau) is a city in the north-east of the Czech Republic and the capital of the Moravian-Silesian Region. It has about 283,000 inhabitants. It lies 15 km (9 mi) from the border with Poland, at the confluences of four rivers: Oder, Opava, Ostravice and Lučina. Ostrava is the third largest city in the Czech Republic in terms of both population and area, the second largest city in the region of Moravia, and the largest city in the historical land of Czech Silesia. It straddles the border of the two historic provinces of Moravia and Silesia. The wider conurbation – which also includes the towns of Bohumín, Havířov, Karviná, Orlová, Petřvald and Rychvald – is home to about 500,000 people, making it the largest urban area in the Czech Republic apart from the capital Prague.

Ostrava grew in importance due to its position at the heart of a major coalfield, becoming an important industrial engine of the Austrian empire. During the 20th century it was known as the "steel heart" of Czechoslovakia thanks to its status as a coal-mining and metallurgical centre, but since the Velvet Revolution (the fall of communism in 1989) it has undergone radical and far-reaching changes to its economic base. Industries have been thoroughly restructured, and the last coal was mined in the city in 1994. However, remnants of the city's industrial past are visible in the Lower Vítkovice area, a former coal-mining, coke production and ironworks complex in the city centre which retains its historic industrial architecture. Lower Vítkovice has applied for inclusion in the UNESCO World Heritage List.

Oder–Neisse line (German: Oder-Neiße-Grenze, Polish: granica na Odrze i Nysie Łużyckiej) is an unofficial term for the modern border between Germany and Poland. The line generally follows the Oder and Lusatian Neisse rivers, meeting the Baltic Sea in the north. A small portion of Polish territory does fall west of the line, including the cities of Szczecin and Świnoujście (German: Stettin and Swinemünde).

In post-war Poland the government described the Oder–Neisse line as the result of tough negotiations between Polish Communists and Stalin. However, according to the modern Institute of National Remembrance, Polish aspirations had no impact on the outcome; rather the idea of a westward shift of the Polish border was adopted synthetically by Stalin, who was the final arbiter in the matter. Stalin's political goals as well as his desire to foment enmity between Poles and Germans influenced his idea of a swap of western for eastern territory, thus ensuring control over both countries. As with before the war, some fringe groups advocated restoring the old border between Poland and Germany.

The Neumark (German pronunciation: [ˈnɔʏmaʁk] ), also known as the New March (Polish: Nowa Marchia) or as East Brandenburg (German: Ostbrandenburg [ˈɔstˌbʁandn̩bʊʁk] ), was a region of the Margraviate of Brandenburg and its successors located east of the Oder River in territory which became part of Poland in 1945 except some villages of former districts of Königsberg in the New March and Weststenberg remained in Germany.

Called the Lubusz Land while part of medieval Poland, the territory later known as the Neumark gradually became part of the German Margraviate of Brandenburg from the mid-13th century. As Brandenburg-Küstrin the Neumark formed an independent state of the Holy Roman Empire from 1535 to 1571; after the death of the margrave John, a younger son of Joachim I Nestor, Elector of Brandenburg, it returned to Elector John George, the margrave's nephew and Joachim I Nestor's grandson. With the rest of the Electorate of Brandenburg, it became part of the Kingdom of Prussia in 1701 and part of the German Empire in 1871 when each of those states first formed. After World War I the entirely ethnic German Neumark remained within the Free State of Prussia, itself part of the Weimar Republic (Germany).

The Sudetes (/suːˈdiːtiːz/ soo-DEE-teez), also known as the Sudeten Mountains or Sudetic Mountains, is a geomorphological subprovince of the Bohemian Massif province in Central Europe, shared by the Czech Republic, Poland and Germany. They consist mainly of mountain ranges and are the highest part of the Bohemian Massif. They stretch from the Saxon capital of Dresden in the northwest across to the region of Lower Silesia in Poland and to the city of Ostrava in the Czech Republic in the east. Geographically the Sudetes are a Mittelgebirge with some characteristics typical of high mountains. Its plateaus and subtle summit relief makes the Sudetes more akin to mountains of Northern Europe than to the Alps.

In the east of the Sudetes, the Moravian Gate and Ostrava Basin separates from the Carpathian Mountains. The Sudetes' highest mountain is Sněžka (Polish: Śnieżka) at 1,603 m (5,259 ft), which is also the highest mountain of the Czech Republic, Bohemia, Silesia, and Lower Silesian Voivodeship. It lies in the Giant Mountains on the border between the Czech Republic and Poland. Praděd (1,491 m/4,893 ft) in the Hrubý Jeseník mountains is the highest mountain of Moravia. Lusatia's highest point (1,072 m/3,517 ft) lies on Smrk mountain in the Jizera Mountains, and the Sudetes' highest mountain in Germany, which is also the country's highest mountain east of the river Elbe, is Lausche (793 m/2,600 ft) in the Lusatian Mountains. The most notable rivers rising in the Sudetes are the Elbe, Oder, Spree, Morava, Bóbr, Lusatian Neisse, Eastern Neisse, Jizera and Kwisa. The highest parts of the Sudetes are protected by national parks; Karkonosze and Stołowe (Table) in Poland and Krkonoše in the Czech Republic.

The Polans (Polish: Polanie; Latin: Polani, Polanos), also known as Polanians or Western Polans (Polish: Polanie Zachodni; Latin: Polani Occidentis), were a West Slavic and Lechitic tribe who inhabited the Warta River basin of the contemporary Greater Poland region starting in the 6th century.

They were one of Central Europe's main tribes and closely related to the Vistulans, Masovians, Czechs and Slovaks. According to Zygmunt Gloger, their name was derived from the word "pole", meaning "field", thus denoting them as "men of the fields".

The Funnel(-neck-)beaker culture, in short TRB or TBK (German: Trichter(-rand-)becherkultur, Dutch: Trechterbekercultuur; Danish: Tragtbægerkultur; c. 4300–2800 BCE), was an archaeological culture in north-central Europe. It developed as a technological merger of local neolithic and mesolithic techno-complexes between the lower Elbe and middle Vistula rivers. These predecessors were the (Danubian) Lengyel-influenced Stroke-ornamented ware culture (STK) groups/Late Lengyel and Baden-Boleráz in the southeast, Rössen groups in the southwest and the Ertebølle-Ellerbek groups in the north. The TRB introduced farming and husbandry as major food sources to the pottery-using hunter-gatherers north of this line.

The TRB techno-complex is divided into a northern group including Northern Germany and southern Scandinavia (TRB-N, roughly the area that previously belonged to the Ertebølle-Ellerbek complex), a western group in the Netherlands between the Zuiderzee and lower Elbe that originated in the Swifterbant culture, an eastern group centered on the Vistula catchment, roughly ranging from Oder to Bug, and south-central groups (TRB-MES, Altmark) around the middle and upper Elbe and Saale. Especially in the southern and eastern groups, local sequences of variants emerged. In the late 4th millennium BCE, the Globular Amphora culture (GAC) replaced most of the eastern and subsequently also the southern TRB groups, reducing the TRB area to modern northern Germany and southern Scandinavia.

The Ślęza (Polish: [ˈɕlɛ̃za]; German: Lohe) is a 78.6 km river in Lower Silesia, southern Poland, a left tributary of the Oder. It starts in the Niemcza Hills (Polish: Wzgórza Niemczańskie), part of the Sudeten Foreland (Przedgórze Sudeckie), and flows near Mount Ślęża through the Silesian Lowland (Nizina Śląska) and enters the Oder in Wrocław.

The most important tributary is the Mała Ślęza ("Small Ślęza"). The most important towns on the river are: Niemcza, Tyniec nad Ślęzą, Jordanów Śląski and Wrocław.

The Pomeranians (German: Pomoranen; Kashubian: Pòmòrzónie; Polish: Pomorzanie), first mentioned as such in the 10th century, were a West Slavic tribe, which from the 5th to the 6th centuries had settled at the shore of the Baltic Sea between the mouths of the Oder and Vistula Rivers (the latter Farther Pomerania and Pomerelia). They spoke the Pomeranian language that belonged to the Lechitic languages, a branch of the West Slavic language family.

The name Pomerania has its origin in the Old Polish po more, which means "Land at the Sea".