Within the city boundaries itself stands the Niš Fortress, which ranks among the most beautiful and best preserved fortresses in the Balkans, built in the late seventeenth century. On the outskirts of Niš is a unique monument - the Skull Tower (Ćele kula) built by the Turks from the skulls and heads of the Serbian warriors who died in the Battle of Čegar in 1809, led by Stevan Sinđelić, against the Turks. After the Turkish victory, this battle was decisive for the failure of the First Serb Uprising.