Ravenna greatly prospered under Roman rule. Emperor Trajan built a long aqueduct at the beginning of the 2nd century. During the Marcomannic Wars, Germanic settlers in Ravenna revolted and managed to seize possession of the city. For this reason, Marcus Aurelius decided not only against bringing more barbarians into Italy, but even banished those who had previously been brought there. In AD 402, Emperor Honorius transferred the capital of the Western Roman Empire from Milan to Ravenna. At that time it was home to 50,000 people. The transfer was made partly for defensive purposes: Ravenna was surrounded by swamps and marshes, and was perceived to be easily defensible (although in fact the city fell to opposing forces numerous times in its history); it is also likely that the move to Ravenna was due to the city's port and good sea-borne connections to the Eastern Roman Empire. However, in 409, King Alaric I of the Visigoths simply bypassed Ravenna, and went on to sack Rome in 410 and to take Galla Placidia, daughter of Emperor Theodosius I, hostage.