Danube, the European river that flows along 10 countries (Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Republic of Moldova, Ukraine) and 4 capital cities (Vienna, Bratislava, Budapest, Belgrade), spills into the Black Sea, through a delta with a total area of 5,050 km² of which only 732 km² belong to Ukraine. In addition, the Danube Delta natural reserve includes the Razim-Sinoe lagoon chain that stretches on 1,145 km², of which 863 km² for the lakes themselves.
Three channels of the Danube form the Delta: Chilia, 104 km long, marks the border with Ukraine, then Sulina, the middle channel, is 71 km long, and last Sfântul Gheorghe, the southern one, which is 112 km long and reveals at the mouth the Sacalin islands, considered the inception of a secondary delta.