The Danube serves as Romania's border river, first with Serbia and then with Bulgaria, for a long distance, but before it reaches the Black Sea, it takes a turn north. The area between this stretch of the Danube the Black Sea is called Dobrogea, and historically this is Bulgarian territory, but fell to the newly formed Romanian union in the 19th century when Russia wanted to keep Bessarabia (what now is the Republic of Moldova). Dobrogea is somewhat hilly, although no peaks reach as high as 500 m.