The Danube Delta is the second largest river delta in Europe, after the Volga Delta, and is the best preserved on the continent. The greater part of the Danube Delta lies in Romania , while its northern part, on the left bank of the Chilia arm, is situated in Ukraine . Its approximate surface area is 4,152 km2 (1,603 sq mi), of which 3,446 km2 (1,331 sq mi) is in Romania. With the lagoons of Razim–Sinoe (1,015 km2 (392 sq mi) with 865 km2 (334 sq mi) water surface), located south of the main delta, the total area of the Danube Delta is 5,165 km2 (1,994 sq mi). The Razim–Sinoe lagoon complex is geologically and ecologically related to the delta proper and the combined territory is listed as a World Heritage Site. The Danube Delta falls within the Pannonian steppe ecosystem of eastern Europe, with Mediterranean influences. As a young region in full process of consolidation, the Danube Delta represents a very favourable place for the development of highly diverse flora and fauna, unique in Europe, with numerous rare species. It hosts 23 natural ecosystems, but due to the extent of wetlands an aquatic environment is prevalent; a terrestrial environment is also present on the higher grounds of the continental levees, where xerophile ecosystems have developed. Between the aquatic and terrestrial environments is interposed a swampy, easily flooded strip of original flora and fauna, with means of adaptation to water or land, depending on the season or hydrological regime. At the contact between freshwater and sea water, some special physical, chemical and biological processes take place, which have led biologists to consider this area as a very different ecosystem called beforedelta. Musura Gulf, north of Sulina, and Saint George Gulf are considered the most representative of this type of ecosystem.