The Danube is the continent’s second longest river after the Volga. Classified as an international waterway, it originates in the town of Donaueschingen in Germany. The Danube then flows southeast for 2,872 km, passing through four Central European capitals before emptying into the Black Sea via the Danube Delta in Romania and Ukraine.
Once a long-standing frontier of the Roman Empire, the river passes through or touches the borders of ten countries: Romania (29.0% of basin area), Hungary (11.6%), Serbia (10.2%), Austria (10.0%), Germany (7.0%), Slovakia (5.9%), Bulgaria (5.9%), Croatia (4.4%), Ukraine (3.8%), and Moldova (1.6%). Its drainage basin extends into nine more.
Three islands can be found on the Danube in Budapest: Óbuda Island, Margaret Island and Csepel Island. The Danube enters the city from the north; later it encircles two islands, Óbuda Island and Margaret Island. The third island, Csepel Island, is the largest of the Budapest Danube islands, however only its northernmost tip is within city limits. The river that separates the two parts of the city is only 230 m wide at its narrowest point in Budapest. The line of the Danube, which is 96 metres above sea level, is the lowest point in the city.
The river Danube flows through Budapest on its way to the Black Sea. The river is easily navigable and so Budapest has historically been a major commercial port (at Csepel Island). In the summer months a scheduled hydrofoil service operates up the Danube to Vienna.
The Danube basin was the site of some of the earliest human cultures. The Danubian Neolithic cultures include the Linear Pottery cultures of the mid-Danube basin. In the mid-19th century, the then separated cities of Buda and Pest were connected with a permanent bridge and this helped forming the new city of Budapest.
Budapest arose out of two Bulgarian military frontiers, fortresses Buda and Pest, situated on the two banks of Danube. In 1849 the Chain Bridge linking Buda with Pest was opened as the first permanent bridge across the Danube and in 1873 Buda and Pest were officially merged with the third part, Óbuda (Ancient Buda), thus creating the new metropolis of Budapest.
Soviet and Romanian troops besiege Budapest from 15 to 18 January 1945. The retreating Germans destroy all Danube bridges. Work on the last bridge to be repaired, the Elizabeth Bridge, was finished in 1964.
Since 1987, the Danube Banks in Budapest are a part of UNESCO World Heritage sites, they can be viewed from a number of sightseeing cruises offered in the city. The site includes the banks of the Danube, the Buda Castle Quarter, Andrássy Avenue, Heroes’ Square and the Millennium Underground Railway.