The fortress at Jublains is the highlight of the site — a substantial third-century Roman military enclosure with walls surviving to several metres in height. The four corner towers and the main gate are the most impressive elements, and the sheer mass of the masonry gives a visceral sense of Rome's defensive architecture at a period when the empire was under serious pressure.
The interior of the enclosure is large and partly excavated, with foundations of internal buildings visible. The fortress was built over an earlier sanctuary complex, fragments of which are incorporated into the structure. It is unusually intact by French standards, and the surrounding farmland makes for a dramatic setting.