The Danube is a river in Central Europe, the continent's second longest after the Volga. Classified as an international waterway, it originates in the town of Donaueschingen which is in the Black Forest of Germany at the confluence of the rivers Brigach and Breg. The Danube then flows southeast for 2,872 km (1,785 mi), 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%), Bulgaria (5.9%), Slovakia (5.9%), Croatia (4.4%), Ukraine (3.8%), and Moldova (1.6%). Its drainage basin extends into nine more. The name Dānuvius is presumably a loan from a Scythian language, or possibly Gaulish. It is one of a number of river names derived from a Proto-Indo-European language word *dānu, apparently a term for "river", but possibly also of a primeval cosmic river, and of a Vedic river goddess (see Danu), perhaps from a root *dā "to flow/swift, rapid, violent, undisciplined." Other river names with the same etymology include Don, Donets, Dnieper and Dniestr. Dniepr (pre-Slavic Danapir by Gothic historian Jordanes) and Dniestr, from Danapris and Danastius, are presumed from Scythian Iranian *Dānu apara "posterior river" and *Dānu nazdya- "anterior river", respectively. The Danube is navigable by ocean ships from the Black Sea to Brăila in Romania and by river ships to Kelheim, Bavaria, Germany; smaller craft can navigate further upstream to Ulm, Württemberg, Germany. About 60 of its tributaries are also navigable. Since the completion of the German Rhine--Main--Danube Canal in 1992, the river has been part of a trans-European waterway from Rotterdam on the North Sea to Sulina on the Black Sea (3500 km). In 1994 the Danube was declared one of ten Pan-European transport corridors, routes in Central and Eastern Europe that required major investment over the following ten to fifteen years. The amount of goods transported on the Danube increased to about 100 million tons in 1987. In 1999, transport on the river was made difficult by the NATO bombing of three bridges in Serbia during the Kosovo War. Clearance of the resulting debris was completed in 2002, and a temporary pontoon bridge that hampered navigation was removed in 2005. At the Iron Gate, the Danube flows through a gorge that forms part of the boundary between Serbia and Romania; it contains the Iron Gate I Hydroelectric Power Station dam, followed at about 60 km downstream (outside the gorge) by the Iron Gate II Hydroelectric Power Station. On 13 April 2006, a record peak discharge at Iron Gate Dam reached 15,400 m³/s. There are three artificial waterways built on the Danube: the Danube--Tisa--Danube Canal (DTD) in the Banat and Bačka regions (Vojvodina, northern province of Serbia); the 64 km Danube--Black Sea Canal, between Cernavodă and Constanţa (Romania) finished in 1984, shortens the distance to the Black Sea by 400 km; the Rhine-Main-Danube Canal (about 171 km), finished in 1992, linking the North Sea to the Black Sea. The Danube Commission is concerned with the maintenance and improvement of the river's navigation conditions. It was established in 1948 by seven countries bordering the river. Members include representatives from Austria, Bulgaria, Croatia, Germany, Hungary, Moldova, Slovakia, Romania, Russia, Ukraine, and Serbia, It meets regularly twice a year. It also convenes groups of experts to consider items provided for in the commission's working plans. The commission dates to the Paris Conferences of 1856 and 1921, which established for the first time an international regime to safeguard free navigation on the Danube.