In the year 47, a Roman general with time on his hands and a restless army decided to dig a canal. The Roman historian Tacitus records that Gnaeus Domitius Corbulo, the commander on the Rhine frontier, kept his legions busy by having them cut a waterway of about twenty-three miles between the Rhine and the Meuse, so that ships could avoid the dangerous open sea. The Fossa Corbulonis, as it is known, probably linked the Old Rhine near Leiden with the Maas estuary, and its line seems to follow the later course of the Vliet, a waterway that still runs between Leiden and Delft. Scholars debate the exact route, but this area, between Voorburg and the Rozenrust district, is a natural candidate.
This part of the Netherlands was once densely Roman. Close by, at Voorburg, lay Forum Hadriani, the only Roman town in the Dutch coastal region, named after the emperor Hadrian and founded in the early second century, and traces of its streets, baths and harbour have been found under the modern suburbs. Many of these remains are under houses and gardens, so what you actually see is very little, a landscape of water, dykes and fields that hides its history in plain sight.
The riding around here is part of what makes the Netherlands a pleasure and a challenge. The country between The Hague and Rotterdam is flat, built up and crossed by canals, motorways and railway lines, and the minor roads are narrow and calm, with clipped hedges and canal views. Cyclists are everywhere and have priority at many crossings, and speed limits are low and enforced with cameras. Bring a rain jacket, as showers arrive suddenly, and note that wind is a serious factor on open stretches. Mornings and evenings are the quietest times, and midday weekend traffic around the big cities can be heavy.
Essesteijn and Kerkehout are small places, and fuel is easy in nearby Leidschendam, Voorburg, Delft or Rotterdam. A short ride south you reach the windmills of Kinderdijk, nineteen mills in a row along a canal, which are also a World Heritage site and a classic Dutch image. Stop at a canal-side cafe, order a coffee and a piece of apple tart, and watch the barges slide past, which is a very Dutch way to follow a Roman general's ditch.