The Skull Tower is one of the most disturbing monuments in Europe, and also one of the most powerful. Standing about three kilometres east of the city centre along the old Istanbul road, this stone structure has 952 human skulls embedded into its walls — the remains of Serbian rebels killed at the Battle of Čegar in 1809, when Serb commander Stevan Sinđelić detonated the Serbian powder magazine rather than surrender, killing himself and hundreds of Ottoman soldiers along with his own men.
The Ottomans built the tower from the skulls as both a trophy and a deterrent. Originally it had skulls on all four sides — 4,000 in total if you count all who were killed — but over the years Serbs stole many skulls to give proper burial to their relatives. What remains is protected inside a small chapel built in the 19th century. Inside you can see the skulls, some still in their stone sockets, along with a portrait of Sinđelić. It is oddly intimate and very quiet.
The tower is a 20-minute walk from the fortress, or a short taxi ride. Opening hours are roughly 9am–6pm in season; the admission is modest.