Danube Delta in the context of "Dobruja Plateau"

The Danube (/ˈdæn.juːb/ DAN-yoob; see also other names) is a river in Europe, the second-longest after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest of Germany south through the Danube Delta in Romania into the Black Sea. A large and historically important river, it was once a frontier of the Roman Empire. In the 21st century, it connects ten European countries, running through their territories or marking a border. Originating in Germany, the Danube flows southeast for 2,850 km (1,770 mi), passing through or bordering Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova, and Ukraine. Among the many cities on the river are four national capitals: Vienna, Bratislava, Budapest, and Belgrade. Its drainage basin amounts to 817,000 km (315,000 sq mi) and extends into nine more countries.

The Danube's longest headstream, the Breg, rises in Furtwangen im Schwarzwald, while the river carries its name from its source confluence in the palace park in Donaueschingen onwards. Since ancient times, the Danube has been a traditional trade route in Europe. Today, 2,415 km (1,501 mi) of its total length are navigable. The Danube is linked to the North Sea via the Rhine–Main–Danube Canal, connecting the Danube at Kelheim with the Main at Bamberg. The river is also an important source of hydropower and drinking water.

Romania is a country located at the crossroads of Central, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to the east, and the Black Sea to the southeast. It has a mainly continental climate, and an area of 238,397 km (92,046 sq mi) with a population of 19 million people. Romania is the twelfth-largest country in Europe and the sixth-most populous member state of the European Union. Europe's second-longest river, the Danube, empties into the Danube Delta in the southeast of the country. The Carpathian Mountains cross Romania from the north to the southwest and include Moldoveanu Peak, at an altitude of 2,544 m (8,346 ft). Bucharest is the country's capital, largest urban area, and financial centre. Other major urban areas include Cluj-Napoca, Timișoara, Iași, Constanța and Brașov.

Settlement in the territory of modern Romania began in the Lower Paleolithic, later becoming the Dacian Kingdom before Roman conquest and Romanisation. The modern Romanian state was formed in 1859 with the unification of Moldavia and Wallachia under Alexandru Ioan Cuza, becoming the Kingdom of Romania in 1881 under Carol I of Romania. Romania gained independence from the Ottoman Empire in 1877, formalised by the Treaty of Berlin. After World War I, Transylvania, Banat, Bukovina, and Bessarabia joined the Old Kingdom, forming Greater Romania, which reached its largest territorial extent. In 1940, under Axis pressure, Romania lost territories to Hungary, Bulgaria, and the Soviet Union. Following the 1944 Romanian coup d'état, Romania switched sides to join the Allies. After World War II, it regained Northern Transylvania through the Paris Peace Treaties. Under Soviet occupation, King Michael I was forced to abdicate, and Romania became a socialist republic and Warsaw Pact member. After the uniquely violent Romanian revolution in December 1989, Romania began a transition to liberal democracy and a market economy.

The Battle of Ongal took place in the summer of 680 in the Ongal area, an unspecified location in and around the Danube Delta near the Peuce Island, present-day Tulcea County, Romania. It was fought between the Bulgars of Asparuh of Bulgaria, who had recently invaded the Balkans, and the Byzantine Empire, which ultimately lost the battle. The battle was crucial for the creation of the First Bulgarian Empire.

Dobruja or Dobrudja (US: /ˈdoʊbrʊdʒə/; Bulgarian: Добруджа, romanized: Dobrudzha or Dobrudža; Romanian: Dobrogea, pronounced [ˈdobrodʒe̯a] or [doˈbrodʒe̯a]; Turkish: Dobruca; Ukrainian and Russian: Добруджа, romanized: Dobrudzha) is a geographical and historical region in Southeastern Europe that has been divided since the 19th century between the territories of Bulgaria and Romania. It is situated between the lower Danube River and the Black Sea, and includes the Danube Delta, the Romanian coast, and the northernmost part of the Bulgarian coast. The territory of Dobruja is made up of Northern Dobruja, which is a part of Romania, and Southern Dobruja, which is a part of Bulgaria.

The territory of the Romanian region Dobrogea is organised as the counties of Constanța and Tulcea, with a combined area of 15,588 km (6,019 sq mi) and, as of 2021, a population of slightly less than 850,000. Its main cities are Constanța, Tulcea, Medgidia, and Mangalia. Dobrogea is represented by dolphins in the coat of arms of Romania.

49°11′30″N 11°15′3″E / 49.19167°N 11.25083°E / 49.19167; 11.25083 (Rhine–Main–Danube Canal)

The Rhine–Main–Danube Canal (German: Rhein-Main-Donau-Kanal; also called Main-Danube Canal, RMD Canal or Europa Canal) is a canal in Bavaria, Germany. Connecting the Main and the Danube rivers across the European Watershed, it runs from Bamberg via Nuremberg to Kelheim. The canal connects the North Sea and Atlantic Ocean to the Black Sea, providing a navigable artery between the Rhine delta (at Rotterdam in the Netherlands), and the Danube Delta in south-eastern Romania and south-western Ukraine (or Constanța, through the Danube–Black Sea Canal). The present canal was completed in 1992 and is 171 kilometres (106 mi) long.

The Bastarnae, Bastarni or Basternae, also known as the Peuci or Peucini, were an ancient people who are known from Greek and Roman records to have inhabited areas north and east of the Carpathian Mountains between about 300 BC and about 300 AD, stretching in an arc from the sources of the Vistula in present-day Poland and Slovakia, to the Lower Danube, and including all or most of present-day Moldava. The Peucini were sometimes described as a subtribe, who settled the Peuke Island in the Danube Delta, but apparently due to their importance their name was sometimes used for the Bastarnae as a whole. Near the sources of the Vistula another part of the Bastarnae were the Sidones, while the Atmoni, another tribe of the Bastarnae are only mentioned in one listing by Strabo.

The earliest Graeco-Roman historians to refer to the Bastarnae imply that they were culturally Celtic. Also consistent with connections to the cultures to their west, later Roman-era sources state directly that they spoke Germanic languages, and could be considered Germanic peoples. In contrast, like other peoples who lived in this geographical region, Graeco-Roman writers also sometimes referred to the Bastarnae as a "Scythian" or "Sarmatian" people, but this was a reference to their location, and customs, rather than a linguistic category. Although largely sedentary, at least one Roman writer, Tacitus, stated that the Bastarnae had adopted some Sarmatian customs. So far, no archaeological sites have been conclusively attributed to the Bastarnae. The archaeological horizon most often associated by scholars with the Bastarnae is the Poieneşti-Lucașeuca culture.

The Chilia branch (Romanian: Brațul Chilia; Ukrainian: Кілійське гирло, romanized: Kiliiske hyrlo) is one of three main distributary channels of the river Danube that contribute to forming the Danube Delta. Lying at the northernmost area of the delta, the distributary creates a natural border between Romania and Ukraine (see Romania-Ukraine border) and is named after the two towns carrying the same name, located across from one another on both banks: Kiliia, on the northern, Ukrainian bank and Chilia Veche (Old Chilia) on the southern, Romanian bank.

The other two main branches of the Danube are the Sulina branch and the Sfântu Gheorghe branch.

In ancient geography, Peuce (Ancient Greek: πεύκη, romanized: peúkē, lit. 'pine tree') is a former island in the Danube Delta, in Scythia Minor (present-day Tulcea County, Romania). It was about the size of the island of Rhodes. The inhabitants of the island were called Peucini (Ancient Greek: Πευκῖνοι).

It was to this island that in the 330s BC the West Thracian Triballian king Syrmus took refuge when pursued by Alexander the Great. Alexander brought ships up the Danube to use in an assault on the island. The attempts failed due to the swift current of the river, steep banks, and fierce defense. Eventually the Macedonians abandoned their attacks on Peuce and instead crossed into the territory of the Getae.