Rainau: town in Germany, known for its Roman auxiliary fort.
Rainau-Buch was an ancient Roman infantry fort (castellum) along the limes of the province of Raetia. It is remarkable because it was exactly square, while most forts are rectangular. The ancient name of the settlement is not recorded.
The fort was probably used by the Cohors III Thracum Veterana, the Third battalion of Thracian Veterans. The area has not been excavated, but using a georadar, archaeologists found out that the fort had the normal buildings: a principia (headquarters) in the center, a praetorium (commander's mansion), six barracks for six centuries of soldiers, stables, et cetera.
Among the finds were military objects and coins. As always, there was a bathhouse outside the fort and a civil settlement in the neighborhood. The bathhouse was to the northeast, on the slope of the hill on which the fort was constructed, and near a little river (now an artificial lake).
The village (vicus) was to the south and east of the fort. It must have been a considerable settlement. The five hundred soldiers must have had their families over there, there must have been pubs and shops. Two thousand inhabitants is not a bad guess.
Fort and town were built in c.165 and evacuated in c.260, when the Alamans occupied the triangle between the Rhine and Danube.