Mouth of the Danube, Romania

Flanked by imposing mountains, one of Europe's principal rivers reaches its end in this Envisat image. The Lower Danube River flows east then north to empty into the Black Sea its triangular Delta, a UNESCO World Heritage Site.

The image covers a major part of the territories of Moldavia, towards image top, along with a thin coastal slice of the Ukraine, Romania, in image middle, and Bulgaria, at the image bottom.

The apparent S-shaped mountain chain dominating the image is made up of the Carpathian Mountains starting top left and the Transylvanian Alps in the middle. There is actually a break in the mountains outside the border of the image, and it is through this gap that the Danube flows east. Towards image bottom are the Balkan Mountains.

The Danube has its source in Germany's Black Forest and is one of Europe's main traffic arteries. It flows through nine European countries for a distance of about 2850 kilometres. The image shows only some of the vast number of the Danube's total tributaries. Also visible are the Prut and Trotus Rivers towards the top of the image, and the Olt River passing through the Transylvanian Alps.

The Lower Danube region is an important European wetland ecosystem that has lost nearly 80% of its wetlands in the last century due to attempts at river dredging, land reclamation and flood control.

Now Romania, Bulgaria, Moldavia and Ukraine have joined together to preserve and restore wetlands with a project called the Lower Danube Green Corridor project, Europe's largest international wetland preservation effort.

Jewel in the crown is the triangle-shaped Danube Delta, projecting out from the coastline due to steady deposition of alluvial material. The Danube Delta was added to the United Nations Educational, Scientific and Cultural Organisation (UNESCO) World Heritage List in 1991. It hosts over 300 species of birds as well as 45 freshwater fish species in its numerous lakes and marshes.

This image was acquired on 28 September 2003 with Envisat's Medium Resolution Imaging Spectrometer (MERIS), working in Full Resolution 300-metre mode.