The Wetterau is a fertile undulating tract, watered by the Wetter, a tributary of the Nidda River, in the western German state of Hesse, between the hilly province Oberhessen and the north-western Taunus mountains. Bettina von Arnim writes of Wetterau in her text Diary of a Child in the chapter "Journey to the Wetterau". The Wetterau is located north of Frankfurt am Main, on the eastern side of the Taunus and south-west of the Vogelsberg. The main part of the region is taken up by the political region Wetteraukreis. The region got its name form the small creek Wetter, but the region is crossed by several other creeks and rivers--for example, the Nidda, Nidder, Horloff and Usa. The Wetterau has a long history and is one of the oldest cultural landscapes in Germany. It was always a very fertile region and was populous from as early as the Neolithic Age. Artifacts from successive civilizations that populated the area also exist. Prominent discoveries are tombs from the Bronze Age, Stufe Wölfersheim or from the Celts, Glauberg. Many historical findings are exhibited in the Wetterau-Museum in Friedberg. The Wetterau was of high strategic relevance for the Roman Empire during its advance into the free Germania. After the end of the Germanic and Gallic wars (58 to 51 BC) a number of Roman forts and roads were built in the Wetterau. A series of fortifications, part of the limes, surrounded the fertile Wetterau region. The region was part of Germania. The first documented reference is from 779 in the Codex Aureus of Lorsch. The economic power of the Wetterau has increased continuously through specific promotion of its urban centres Frankfurt am Main, Wetzlar, Gelnhausen and Friedberg since Frederick I, Holy Roman Emperor. The cities with their magnificent buildings were important bases for the royal travels and central places for exercising royal rights in the areas of economy and jurisdiction. The economic power was reflected in the right for coinage of the Lords of Hagen-Münzenberg and the urban right to hold markets.