After abandoning the Alblimes (a Limes generally following the ridgeline of the Swabian Jura) around 150 AD, Aalen's territory became part of the Roman Empire, in direct vicinity of the then newly erected Rhaetian Limes. The Romans erected a castrum to house the cavalry unit Ala II Flavia milliaria; its remains are known today as Kastell Aalen. The site is west of today's town centre at the bottom of the Schillerhöhe hill. With about 1,000 horsemen and nearly as many grooms, it was the greatest fort of auxiliaries along the Rhaetian Limes. There were Civilian settlements adjacent along the south and the east. Around 260 AD, the Romans gave up the fort as they withdrew their presence in unoccupied Germania back to the Rhine and Danube rivers, and the Alamanni took over the region. Based on 3rd- and 4th-century coins found, the civilian settlement continued to exist for the time being. However, there is no evidence of continued civilization between the Roman era and the Middle Ages.
There is a Limes Museum located adjacent the Kastell.
References:The Château de Foix dominates the town of Foix. An important tourist site, it is known as a centre of the Cathars. Built on an older 7th-century fortification, the castle is known from 987. In 1002, it was mentioned in the will of Roger I, Count of Carcassonne, who bequeathed the fortress to his youngest child, Bernard. In effect, the family ruling over the region were installed here which allowed them to control access to the upper Ariège valley and to keep surveillance from this strategic point over the lower land, protected behind impregnable walls.
In 1034, the castle became capital of the County of Foix and played a decisive role in medieval military history. During the two following centuries, the castle was home to Counts with shining personalities who became the soul of the Occitan resistance during the crusade against the Albigensians.