Rhine–Main–Danube Canal in the context of "Kelheim"

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.

Nuremberg (/ˈnjʊərəmbɜːrɡ/, NURE-əm-burg; German: Nürnberg [ˈnʏʁnbɛʁk] ; in the local East Franconian dialect: Nämberch [ˈnɛmbɛrç]) is the largest city in Franconia and the second-largest city in the German state of Bavaria. Its 544,414 (2023) inhabitants make it the 14th-largest city in Germany.

Nuremberg sits on the Pegnitz, which carries the name Regnitz from its confluence with the Rednitz in Fürth onwards (Pegnitz→ Regnitz→ Main→ Rhine→ North Sea), and on the Rhine–Main–Danube Canal, that connects the North Sea to the Black Sea. Lying in the Bavarian administrative region of Middle Franconia, it is the largest city and unofficial capital of the entire cultural region of Franconia. The city is surrounded on three sides by the Nürnberger Reichswald [de], a large forest, and in the north lies Knoblauchsland [de] (garlic land), an extensive vegetable growing area and cultural landscape.

The Danube–Black Sea Canal (Romanian: Canalul Dunăre–Marea Neagră) is a navigable canal in Romania, which runs from Cernavodă on the Danube river, via two branches, to Constanța and Năvodari on the Black Sea. Administered from Agigea, it is an important part of the waterway link between the North Sea and the Black Sea via the Rhine–Main–Danube Canal. The main branch of the canal, with a length of 64.4 km (40.0 mi), which connects the Port of Cernavodă with the Port of Constanța, was built in 1976–1984, while the northern branch, known as the Poarta Albă–Midia Năvodari Canal, with a length of 31.2 km (19.4 mi), connecting Poarta Albă and the Port of Midia, was built between 1983 and 1987.

Although the idea of building a navigable canal between the Danube and the Black Sea is old, the first concrete attempt was made between 1949 and 1953, when the communist authorities of the time used this opportunity to eliminate political opponents, so the canal became notorious as the site of labor camps, when at any given time, between 5,000 and 20,000 detainees, mostly political prisoners, worked on its excavation. The total number of prisoners used as labor force during this period is unknown, with the total number of deaths being estimated at several tens of thousands. The construction works of the Danube–Black Sea Canal were to be resumed 20 years later, in different conditions.