In the 1st Century BC Celtics lived on the Swabian Alb. That is why there was a Celtic fortification found with a total area of 1.662 hectares. It is known by the name "Heidegraben". This fortification had a inside and outside defensive ring. The "Heidegraben" is not only the largest Celtic fortification in Germany but also one of the largest in Europe.
However only a small percentage of it has been studied and discovered. Nevertheless, a lot of jewellery and other findings lead to the assumption that it was a lively trading city beyond national borders. Today. the "Heidegraben" is part of the biosphere reserve on the Swabian Alb.