The Crveni krst concentration camp (German Red Cross) was located in the north-western suburb of the Serbian city of Niš and was built during the Second World War in the military administrative region of Serbia.
It is estimated that around 30,000 people were held in the camp and around 12,000 people were murdered, most of whom were citizens of the city of Niš. 10,000 people were executed on Bubanj Hill alone, which was in the immediate vicinity of the concentration camp, where the current memorial is located. Many of the detainees were taken to other concentration camps such as Sajmište concentration camp or other camps in Europe.
Source: Wikipedia