Celt , Any member of an early Indo-European people who spread over much of Europe from the 2nd millennium to the 1st century bc. They were absorbed into the Roman Empire as Britons, Gauls, Boii, Galatians, and Celtiberians. Early archaeological evidence (c. 700 bc) comes from the Hallstatt site in Austria. People of this Iron Age culture controlled trade routes along the Rhône, Seine, Rhine, and Danube rivers. As they moved west, Hallstatt warriors introduced the use of iron, which helped them dominate other Celtic tribes. By the mid 5th century bc, the La Tène culture emerged along the Rhine and moved into eastern Europe and the British Isles. Celts sacked Rome c. 390 and raided the whole peninsula, then settled south of the Alps (Cisalpine Gaul) and menaced Rome until they were defeated in 225 bc. In the Balkans, they sacked Delphi in 279 but were defeated by the Aetolians. They crossed to Anatolia and looted until they were subdued by Attalus I about 230 bc. Rome controlled Cisalpine Gaul by 192 and in 124 took territory beyond the Alps. In Transalpine Gaul, from the Rhine and the Alps west, the Celts were pressed by Germanic tribes from the west and Romans from the south. By 58 Julius Caesar had begun campaigns to annex all of Gaul. Celtic settlement of Britain and Ireland is deduced from archaeological and linguistic evidence. The Celtic social system comprised a warrior aristocracy and freemen farmers; Druids, with magico-religious duties, ranked higher than warriors. They had a mixed farming economy. Their oral literary composition was highly developed, as was their art; they manufactured gold and silver jewelry, swords and scabbards, and shields inlaid with enamel.