 Golubac 's early history is uncertain . Inscriptions and evidence of older defensive structures in the area show the presence of a Roman settlement , sometimes named " Columbaria , " long before the creation of Golubac . From 803 to 1018 , the area belonged to the First Bulgarian Empire , to Byzantium from then until 1193 , and the Second Bulgarian Empire until 1257 . The area remained in Bulgarian hands from then until the Ottoman conquest in the 15th century , with control of the region changing many times between Hungarians , Bulgarians and Serbs before then . It is also unclear whether the medieval fortress was built by Bulgarians , Serbs or Hungarians , or how many towers it had originally . However , an Orthodox chapel built as part of one tower shows that it , at least , was built by a local noble . There is also uncertainty about when construction started , although it is generally agreed that the majority of the fortress was built early in the 14th century . 
