The native tribes of the wider region of the Lower Danube were for the first time united under King Burebista who ruled from around 80 or 70 BC. He defeated the Boii and the Taurisci, who dwelled in the Middle Danube region, around 60 BC, subdued the Scordisci and made plundering raids against Thracia, Illyricum and Macedonia in the subsequent years. In the middle of the 1st century BC, his empire was bordered by the Middle Danube, the Northern Carpathians, the Black Sea and the Balkan Mountains. Its center was located in the Orăştie Mountains where Burebista had a number of fortifications erected. This forts were built by Greek craftsmen who introduced the use of chiseled stone.