The Danube Delta is situated in the eastern part of Romania, in the Tulcea county.
The Danube Delta has the third ecological significance among the 300 UNESCO reserves in the world. Through UNESCO resolution of 02.02.1999, the Danube Delta reserve received the international certificate of  Biosphere Reserve.
The Danube Delta has a surface of 5.640 km²,  the second largest delta in Europe. The surface that is included in the Danube Delta Biosphere Reserve (D.D.B.R.) is of 4.178 km², only 3.446 km² of which are on Romanian territory.
The Razim-Sinoe lagoon system is also included in the Danube Delta and it comprises Razim, Golovita, Zmeica and Sinoe lakes. About the Lake Razim`s name there are more variants: its name comes from that of the Russian orthodox of old rite revolutionist Stepan Razim that was killed on the lake`s borders. The name of Razelm was used by the Turks to designate this lake.
The Danube Delta was formed at the Danube river mouth that flows in the Black Sea. The river is the second in length in Europe after the Volga and it springs from the Black Forest Mountains (Schwarzwald) in Germany and travels 2.860 km until its river mouth, crossing 17 countries. Due to the mud deposits carried by the river, the delta`s surface has grown in time (it grows with 40 m per year), most of its relief is formed of channels, lakes, sand dunes.
On the Tulcea county territory the Danube flows in the Black Sea through three river branches: Kilia in the north that has a length of 115 km, a depth of 39 m and the Tulcea Branch (19 km in length) that is divided at the Sulina Ceatal in two: Sulina Branch, 64 km length and 26 m depth that traverses the middle of the delta and Saint George`s Branch (64 km in length, 26 m in depth) in the south.