The Danube Delta is the second largest river delta in Europe. The Romanian Danube Delta Biosphere Reserve (580,000 ha) is situated northwest of the Black Sea in Eastern Europe. Four geographic divisions can be distinguished; the Danube Delta, the Razim-Sinoe lagoon complex,the Isaccea-Tulcea sector of the Danube flood plain and the shallow marine waters. The Danube Delta is a low alluvial plain, mostly covered by wetlands and water. It consists of an intricate pattern of marshes, channels, streamlets and lakes. The average altitude is 0.52 m, with 20% of the territory below sea level, and more than half not exceeding one meter in altitude. Dunes on the most extensive strand plains of the delta (Letea and Caraorman strand plains) stand higher (12.4 m and 7 m respectively). The largest lakes are Dranov (21.7 km²), Roșu (14.5 km²), Gorgova (13.8 km²).