The first traces of human civilization in Geneva, discovered on the shores of Lake Geneva , date from around 3000 BC. The hill of the Old City, however, was not inhabited until 1000 BC. Later, when Rome conquered Geneva, it was defended by a small Celtic tribe. In 58 BC, Julius Caesar drove off an attack by the Helvetii. At the height of the Roman Empire, around 400 AD, Geneva was granted its own bishop.