The monument to the Unknown Hero on Avala adornes for almost eight decades the city of Belgrade and became one of its trademarks. However, the thing less known is that this monument was erected on the site of the former medieval fortress Žrnov, completely destroyed. The remains of the fortress several thousand years old, were removed on the orders of King Aleksandar I Karadjordjevic.

There is no precise date when the fortress Žrnovo was built, according to some historians, it dates back to Roman times, to control the way to Singidunum. But it is almost certain that the fortress was built in the time of the despot Stefan Lazarevic.

During World War I, in 1915, under Žrnov, in the battle between Serbian and German armies a fifteen year old Serbian boy was killed. Germans buried him and on the wooden cross over the grave left the inscription “Ein unbekannter serbischer soldat” or “An unknown Serbian soldier.” Many investigated about the identity of the soldier, but none has been able to figure out who he really was. Many years have passed since the Unknown Hero was killed, but he has become a synonym for all the sacrifices that Serbia maked in the First World War.

The monument to the Unknown Hero is built from black granite, designed to represent the mausoleum, with four caryatids presented as women in traditional costumes. These eight statues symbolize the mother of soldiers, the nations and regions of the Kingdom of Yugoslavia : Šumadija, Voivodina, Montenegro, Kosovo, Dalmatia, Zagorje, Slovenia and Macedonia. The monument was erected in 1938 and represents the work of the most famous sculptor of the time – Ivan Mestrovic.

On February 15 each year, on the National Day of Serbia, people pay tribute to all Serbian soldiers killed in the wars.