Grinnes: Roman fort on the river Waal, perhaps identical to modern Rossum in the Netherlands.
Torques from Rossum
Roman finds near Rossum may belong to a fort named Grinnes, but excavation is impossible because the site is too close to the rivers Waal and Meuse, and was probably destroyed. Not a single artifact can be dated before 70 CE, which confirms the words of the historian Tacitus that this fort was founded by Quintus Petillius Cerialis after the Batavian revolt.
On the other hand, there have been finds from the final phase of the Iron Age, so the site may have been continuously occupied after all, and the remains of the intermediary period may have been washed away.