After the conquest of Gaul by the Romans in 50 B.C. the Rhine became part of the border of the Roman Empire. The Romans erected camps and forts along the river from the Alps down to the North Sea. The history of Speyer began with the construction of one of these camps around 10 BC for a 500-man–strong infantry group and also intended as a base for further conquests to the east of the Rhine. The decisive factor for the location were the wedge-shaped high river banks, of which the tip pointed far east into the floodplain of the Rhine. Thus, the settlement, although right by the river, was safe from floods. Due to the river's extensive meandering such possibilities were very rare between Basel and Mainz. The first fort was erected in the eastern section of today's Maximilianstrasse between the Kleine Pfaffengasse and the Grosse Himmelsgasse. The southern moat was located along the Kleine Pfaffengasse.
