The Skull Tower (Serbian: Ћеле Кула, Ćele Kula, Turkish: Kelle Kulesi) is a monument to 19th century Serbian rebels. It is situated 60km from Sokobanja, in Niš, on Constantinople road, on the old Constantinople road leading to Sofia. The tower was built with the skulls of the Serbs killed during the 1809 Battle of Čegar by the order of Ottoman Sultan Mahmud II. In front of the chapel stands the monument to Sinđelić, and a small relief depicting the battle, both from 1937. The monument commemorating the battle in the form of a guard tower was built in 1927 on Čegar Hill by Julian Djupon. The lower part is made out of stone from the Niš fortress. Skull Tower was declared Monument of Culture of Exceptional Importance in 1979, and it is protected by Republic of Serbia.