The black line indicates the east wall of the "Palace" discovered by Th. Vacquer in 1845. North is at the top.
Located at the western tip of the Île de la Cité, the Palace occupied an area of at least one hectare. Three of its sides consisted of the city's ramparts and the fourth wall was nearly a metre thick. This is clearly a military building, and is probably where Julian was proclaimed emperor by his troops. Even if later became the Merovingian and Capetian royal palace-before making way for the current Palais de Justice-it was not an imperial palace in the strict sense of the term. Rather, it was a temporary residence for a soldier-emperor who was always on military campaign.
Was the building used for other purposes? Specifically, could the emperor's troops have been stationed there? It is likely that the majority of the soldiers were based in a camp located off the island, near an exercise field spoken of by Ammianus Marcellinus. It is also tempting to see the "Palace" as a sort of well-protected arsenal, strategically located next to the river. Or perhaps it held shops or warehouses, also mentioned by Ammianus Marcellinus ?