The Struma or Strymónas (Bulgarian Струма, pronounced [ˈstruma], Greek Στρυμόνας [striˈmonas], Turkish (Struma) Karasu 'black water') is a river in Bulgaria and Greece. Its ancient name was Strymōn (Greek: Στρυμών [stryˈmɔːn]). Its catchment area is 10,800 km². It takes its source from the Vitosha Mountain in Bulgaria, runs first westward, then southward, enters Greek territory at the Kula village. In Greece it is the main waterway feeding and exiting from Lake Kerkini, a significant centre for migratory wildfowl. The river flows into the Strymonian Gulf in Aegean Sea, near Amphipolis in the Serres regional unit.