For a few hundred years, the mouth of the Rhine was the edge of the world. West of Leiden, the river that once spilled into the North Sea along the Old Rhine channel marked the frontier of the Roman Empire, and the legions kept a line of forts along its banks. Valkenburg, a small village near the coast north of The Hague, was one of them, and the site of a fort known by the name Praetorium Agrippinae, which is the Roman name that archaeologists give to the Valkenburg fort. It sat on the south bank of the river, with a harbour, a bridge or two, and a settlement of traders and soldiers around it, and the finds from the area include timbers, shoes, and tools preserved in the damp clay.
The Lower Germanic Limes, as the whole frontier is called, was inscribed as a World Heritage site in 2021, and the Valkenburg sites form a part of it. There is very little to see above ground. The Rhine moved, the coast changed, and later centuries piled sand and peat over the Roman land, so the experience is subtle, and you read the landscape through the information panels, the museum displays and your imagination. Still, standing on a dyke at sunset with the line of the old river at your feet is an unexpectedly strong feeling.
The riding here is flat and windy, in the classic way of the western Netherlands. Narrow roads run along dykes and canals between grass fields, with cows, sheep and the occasional windmill, and the sky is huge. The surface is smooth, the limits are strict and speed cameras are frequent, so keep to the numbers. Cyclists have priority in practice, and they are everywhere, so ride with courtesy and patience. A headwind can be a serious tiring force, and rain showers come and go quickly. Early morning and the evening are the most beautiful times, and spring brings the tulip fields of the nearby bulb district.
Valkenburg and Hoge Mors are small places with a few thousand people, and fuel is easy within a short ride, in Katwijk, Leiden or The Hague. Dutch bakeries sell good coffee and a slice of apple pie, and the beaches at Katwijk are a short run to the west.