The period of prehistory distinguished technologically by the use of iron. This was first mastered on a large scale by the Hittites in Anatolia between 1500 and 1200 bc, and spread to the Aegean, and thence to south-east and central Europe and Italy. The spread was slow across Europe, as it only gradually replaced bronze. In Africa the Iron Age immediately followed the Stone Age, bronze entering much later. In America, iron was not discovered before being introduced from Europe. The culture of the early European Iron Age (c.750–450 bc) is known as Hallstatt culture, after the site of a prehistoric cemetery near the town of Hallstatt in Austria. At first cremation was the rule, as were flat or low graves, though later the tumulus or raised barrow became standard. As iron became common, burial was used as well as cremation, and the quality of the characteristic geometric-style pottery degenerated. It was superseded by the late Iron Age Celtic La Tène culture, named after an archaeological site near Lake Neuchâtel, Switzerland. La Tène culture began in c.450 bc, when the Celts came into contact with Greek and Etruscan civilization. It lasted, with various developments, until the 1st century bc, when most of the Celts came under the aegis of the Roman empire. A distinct artistic style developed, characterized by such devices as s-shapes, spirals, and circular patterns, which show that La Tène artists were influenced by Greek and Etruscan motifs. The finest examples of La Tène art display a remarkable mixture of abstract and figurative animal and vegetable representations. The society fragmented from about 400 bc but certain items including long iron swords, decorated scabbards, belts, shield bosses, hammers, sickles, and plough shares continued to be found throughout the area. Invaders from the north at first brought new artefacts and artistic devices, but the culture eventually disappeared.