During the archaeological exploration of the fortress in the 2015-2018 period, it was discovered that the modern fortress was predated by the much older architectural elements. Though not mentioned in historical records, there were artifacts pointing out to the pre-Roman habitation of the Celts. Close to the modern fortress, the remains of the Celtic fortified settlement Opidum have been found. Based on this, and the description of the Danube's bank in ancient texts which corresponds to the Ram's geography, some scholars suggested that this may be the location where Alexander the Great encountered the Celtic delegation in the 4th century BC.