The Great Morava (, ) is the final section of the Morava (), a major river system in Serbia. Etymology According to Predrag Komatina from the Institute for Byzantine Studies in Belgrade, the Great Morava is named after the Merehani, an early Slavic tribe who were still unconquered by the Bulgars during the time of the Bavarian Geographer. However, after 845, the Bulgars added these Slavs to their societas (they are last mentioned in 853). Length The Great Morava begins at the confluence of the South Morava and the West Morava, located near the village of Stalać, a major railway junction in Central Serbia. From there to its confluence with the Danube northeast of the city of Smederevo, the Velika Morava is 185 km long. With its longer branch, the West Morava, it is 493 km long. The South Morava, which represents the natural headwaters of the Morava, used to be longer than the West Morava, but due to the regulations of river bed and melioration, it is shorter nowadays. At one time (regulations were made on all three branches making them shorter) the Morava was over 600 km long. Today, the most distant water source in the Morava watershed is the source of the Ibar River, the right and longest tributary of the Zapadna Morava, originating in Montenegro, which gives the Ibar-West Morava-Great Morava river system a length of 550 km, which still makes it the longest waterway in the Balkan Peninsula. Geography The drainage basin of the Velika Morava is 6,126 km2, and of the whole Morava system is 38,207 km2 (of that, 1,237 km2 are in Bulgaria and 44 km2 are in the Republic of Macedonia). This drainage basin covers 42,38% the area of Serbia. Velika Morava flows through the most fertile and densely populated area of Central Serbia, called the Morava river valley or Pomoravlje. Pomoravlje was formed in a fossil bay of a vast, ancient Pannonian Sea which dried out 200,000 years ago. Through about half of its length it passes through beautiful Bagrdan gorge (Bagrdanska klisura). In past centuries, it was known for its seemingly endless forests, but there is almost nothing left today of those old woods. It flows into the Danube between the villages of Kulič & Dubravica, in the coal mining basin of Kostolac, one of two major mines in its drainage basin (the other one being Resava coal basin, in