Friedberg sits atop a basalt plateau overlooking the Usa and has been populated at least since Roman times. The relics of a Mesolithic settlement have been found in Bruchenbrücken, a suburb of Friedberg. Castle Hill was the location of a Roman military camp, part of the "limes" or border fortifications and presumably identical with the "castellum in monte tauno" that is quoted in Roman records during the 1st century AD, though this is still under discussion. Ruins of the camp, as well as other Roman ruins, have been found and conserved, such as the remains of Roman public baths ("thermae"). The Roman settlement was abandoned during the retreat of the Romans on the Rhine frontier by 260 AD. The crown and ports atop the Adolfsturm (the most prominent feature of the Friedberg castle) was restored during the 1980s.