What does a river do? As anyone who has lived by one knows, rivers structure human worlds in many ways. This project explores the role of Europe’s greatest river in the formation of new societies, in and after the last centuries of the Roman Empire in the West (150–700 AD). The Danube occupied a complex place in the late Roman Empire. Its banks were home for thousands of people. It formed the Empire’s boundary for much of its existence. It was the major axis of communication across central Europe, facilitating the movement of people, things and ideas.