Their main oppidum (16–20 hectares) until the Roman period, corresponding to the modern town of Vermand, was situated on a promontory east of the Omignon river. Fortifications and continuous occupation emerged relatively late on the site, just before or during the Gallic Wars (58–50 BC), and it probably served only as a temporary refuge until the Roman invasion of Belgica. Some have also proposed that it was erected as a military camp by Belgic auxiliaries serving in the Roman army. The site remained densely occupied from the Augustan era until the beginning of the 5th century AD.