During the Battle of Čegar in 1809, several hundred Serbian revolutionaries blew themselves up rather than surrender to the Turkish army. Later, near the site of the battle in the city of Niš, the Turks constructed a ten-foot-tall tower embedded with the skulls of 952 fallen Serbs.
The Serbian heads were originally in the possession of Sultan Mahmud II, leader of the Ottoman empire, but were sent back to Niš for construction of the tower. Structures like this were often built to intimidate the Turks' enemies, and this one was designed to discourage further rebellion against the Sultan's rule.
Photo: Kulmalukko via Wikivoyage WTS
When the Serbs finally retook Niš in 1878, they built a chapel around Ćele-kula (Skull) Tower, and today it's a popular tourist attraction... but the structure now contains only 54 of the original skulls. Many were reclaimed by the soldiers' families, while others were stolen as souvenirs. The glass-encased skull shown below is believed to be that of Stevan Sinđelić, leader of the doomed revolutionaries.
Photo: Pudelek via Wikimedia Commons