Under the emperors Domitian (81-96 AD), Trajan (98-117 AD) and Hadrian (117-138 AD) the Roman Limes formed the boundary with the tribes to the north. This defensive line bisected the south of Franconia and describes an arc through the region whose northernmost point was located at today's Gunzenhausen. To oversee it, the Romans built several forts, such as Biriciana near Weißenburg or Ruffenhofen at the foot of the Hesselberg. However, by the middle of the third century, the Limes border could no longer be maintained because by 250 AD the Alemanni occupied the areas south of the Limes as far as the Danube.