The most significant feature of Tulcea County is the Danube Delta, which occupies about 1/3 of the entire surface and is located in the North-East side of the county. The Delta has three main branches: the Sulina branch (the only one navigable by large ships) in the middle, the Chilia branch in the North (the border with Ukraine) and the Sfântu Gheorghe branch (Saint George) in the South.