The north German coast and the foot of the Danish peninsula seem to have been occupied by peoples speaking a Germanic language from the earliest times.
To the east Baltic-speaking tribes shared the land with the non-Indo-European speaking ancestors of the Finns and the Estes. South and east, into what are now the Czech Republic, Austria and Hungary, peoples speaking the Illyrian language seem to have been dominant. Along the upper Danube and the upper Rhine, Celtic speaking peoples were beginning their consolidation.
About 1000 BCE the Germans were confined to southern Sweden, the Jutland peninsula, the Danish isles and the country from the Ems to the Oder. Their southern boundary was the Teutoburger Wald and the Harz mountains.
At the dawn of the historical period, Germania was on the right bank of the Rhine and bounded to the south by the Hyrcanian forest (from perca "oak" ) that stretched unbroken from the Hunsrück to modern Slovakia.
To the south and west, Celtic speaking peoples were in their most decisive phase of formation with their political and cultural centre of gravity on the east bank of the Rhine. The Celtic language was spread to the lower Rhine, into Gaul, Spain, northern Italy, the British Isles, and most of central Europe to the mouth of the Danube.
In Caesar's time (mid first century B.C.E.) German peoples had penetrated the forest barrier They had started to occupy the Main valley and lands further south on the right bank of the Rhine. Caesar's first confrontation with the Germans was with Ariovistus, king of the Suebi, who had led a confederation of tribes across the Rhine and who occupied what is now Alsace.
In 90 C.E. the Roman imperial organisation created two German provinces.
Germania prima Upper Germany, (Oberdeutschland) with its capital at Mainz (Mogontiacum), was on the both banks of the Rhine and occupied the re-entrant angle formed by the upper courses of the Rhine and the Danube. Its northern and eastern frontiers were defended by a palisade and ditch that joined the frontier wall built in Rhaetia to the north of the Danube. On the left bank of the Rhine the province included the region around Besancon, Alsace and the Pfalz extending along the Rhine bank as far north as the Eiffel.
Germania secunda Lower Germany, (Niederdeutschland) included the northern parts of modern Belgium and south Holland. Its northern frontier followed the Rhine and the Ijssel to the Zuider Zee (lake Flevo).
Military control was centred at Vetera (Xanten). The provincial capital was at Colonia Agrippina (Köln).