Vindobona (from Gaulish windo- "white" and bona "base/bottom") was a Roman military camp on the site of the modern city of Vienna in Austria. The settlement area took on a new name in the 13th century, being changed to Berghof, or now simply known as Alter Berghof (the Old Berghof).Around 15 BC, the kingdom of Noricum was included in the Roman Empire. Henceforth, the Danube marked the border of the empire, and the Romans built fortifications and settlements on the banks of the Danube, including Vindobona with an estimated population of 15,000 to 20,000.