 The Golubac Fortress ( Serbian : <unk> <unk> or <unk> grad , Hungarian : <unk> <unk> , Bulgarian : <unk> , Romanian : Cetatea <unk> , Turkish : <unk> <unk> ) was a medieval fortified town on the south side of the Danube River , 4 km downstream from the modern @-@ day town of Golubac , Serbia . The fortress , which was most likely built during the 14th century , is split into three compounds which were built in stages . It has ten towers , most of which started square , and several of which received many @-@ sided reinforcements with the advent of firearms . 
