Fossil finds show that the region was already settled by primitive man, Homo erectus, in the middle Ice Age about 600,000 years ago. Probably the oldest human remains in the Bavarian part of Franconia were found in the cave ruins of Hunas at Pommelsbrunn in the county of Nuremberg Land. In the late Bronze Age, the region was probably only sparsely inhabited, as few noble metals occur here and the soils are only moderately fertile. In the subsequent Iron Age (from about 800 B.C.) the Celts become the first nation to be discernible in the region. In northern Franconia they built a chain of hill forts as a line of defence against the Germanii advancing from the north. On the Staffelberg they built a powerful settlement, to which Ptolemy the name oppidum Menosgada, and on the Gleichberge is the largest surviving oppidum in Central Germany, the Steinsburg. With the increased expansion of Rome in the first century B.C. and the simultaneous advance of the Elbe Germanic tribes from the north, the Celtic culture began to fall into decline. The southern parts of present-day Franconia soon fell under Roman control; however, most of the region remained in Free Germania. Initially Rome tried extend its direct influence far to the northeast; in the longer term, however, the Germanic-Roman frontier formed further southwest.