Niš Fortress is a fortress in the city of Niš, Serbia. It is a complex and important cultural and historical monument. It rises on the right bank of the Nišava River, overlooking the area inhabited for longer than two millennia. It was protected by law in May 1948 as it was declared a cultural site of great significance. The current condition of the fortress lists it as one of the best preserved fortifications of this kind in Serbia as well as on the Balkan Peninsula. The existing fortification is of Ottoman Turkish origin, dating from the first decades of the 18th century (1719–1723). It is well known as one of the most significant and best preserved monuments of this kind in the mid-Balkans. The Fortress was erected on the site of earlier fortifications – the ancient Roman, Byzantine, and later yet Medieval forts. During World War I it was occupied by Bulgarians who turned it into a prison where Serbian patriots were imprisoned and tortured.