Dark tourism - Balkan 

22`Niš's premier dark history attractions feature three specific locations: Red Cross Concentration Camp (Crveni Krst): A chilling WWII Gestapo camp where approximately 30,000 prisoners were held. It is notoriously famous for being the site of the first mass prison break in occupied Europe in 1942. You can still see poignant inscriptions scratched into the cell walls by inmates.Bubanj Memorial Park: Located on a forested hill on the southern outskirts of the city, this monument commemorates the mass execution of more than 10,000 Serbs, Jews, and Roma by the Nazis. The site features three massive, clenched-fist concrete monoliths representing the resistance of men, women, and children. Skull Tower (Ćele Kula): A gruesome 19th-century monument constructed by the Ottoman Turks using the severed skulls of fallen Serbian rebels following the Battle of Čegar. Once a stark warning to the local population, it is now housed inside a chapel as a somber memorial.
Practical Details: Tickets: You can purchase a combined ticket that grants access to the Concentration Camp, Skull Tower, and the National Museum for around 200–300 RSD (roughly €2 to €3). 
Ask for price >