Go west from Nijmegen along the river and you are following the northern frontier of the Roman Empire. The Lower German Limes ran for about four hundred kilometres along the Rhine, from near Bonn to the North Sea at Katwijk, and for roughly three hundred years it marked the edge of the empire. It was never a wall. It was a line of forts, watchtowers, roads, harbours and ports along a river, defended by auxiliary troops and patrolled by boat, and almost all of it lies buried under fields, villages and dikes. In 2021 it was added to the World Heritage list.
The west side of the Kops Plateau is a good place to understand this. From here the old fortress looked out across the river valley, and the road west ran along the south bank of the Waal and then the Rhine. Today there is a modern equivalent: dike roads and country lanes run along the old river line through Arnhem, Wijk bij Duurstede, Utrecht, Leiden and the dunes at the coast. Riding it is a Dutch pleasure, with polder views, windmills, farms with thatched roofs, and the river never far away.
Do not expect hills or hairpins. This is a gentle country that rewards patience, with low speed limits, cameras and roundabouts at every junction. Wind off the North Sea is the main challenge, and a headwind on an exposed dike can be tiring. Fuel is easy in the towns, and Nijmegen itself has every service you could want.
Along the way you can visit small museums in places such as Wijk bij Duurstede and Vechten, which show Roman finds and explain the frontier. The Kops Plateau is a good beginning for the journey, because it tells you who these soldiers were, where they came from and why they stayed.
Spring is the best season, with fruit blossom in the Betuwe, followed by the long light evenings of early summer. Autumn brings migrating geese, and winter can bring floods, which in a way is the Rhine reasserting its old rights. Bring waterproofs, because rain arrives without warning, and a thermos for the cold dike tops.