Rendsburg is a town made by a ditch, and what a ditch. The Kiel Canal, known in German as the Nord-Ostsee-Kanal, was opened in 1895 as the Kaiser-Wilhelm-Kanal, cutting across the base of the Danish peninsula so that ships need not sail all the way around Skagen. It is still the busiest artificial seaway in the world by number of ships, and standing on the bank at Rendsburg you can watch container vessels, tankers and ferries glide past at what looks like walking pace, a few metres from the road. A quiet fact makes it more striking: the surrounding land is so flat and low, only a few metres above sea level, that the ships seem to be sailing through meadows.
The landmark is the high railway bridge of 1913, a great steel loop that lifts the line high enough to clear the shipping, and beneath it hangs a transporter ferry, a platform on cables that carries cars and bikes across the canal. It is one of very few still working in the world, and riding onto it is a genuine curiosity. The old road tunnel under the canal, from 1961, is the other crossing, and several ferries operate free of charge along the canal. Beside the water is the old town on the Eider river, a tidy mix of garrison buildings and brick houses dating to the time when the Danish crown fortified the place.
The riding in this region is gentle, flat and often windy, a world of long straight roads, hedge-lined fields called knicks, reed beds and quiet villages. It is not a place for hairpins, but it has a generous, slow rhythm, and the canal-side roads on both banks are very pleasant on a bike, with the ships alongside. Wind from the North Sea can be strong, and cross-winds on the bridges can surprise you.
Rendsburg has nearly thirty thousand people, so you will find fuel, bakeries, fish sandwiches and cafes, and the neighbouring town of Büdelsdorf has the old iron works turned into an art venue. Try a Fischbrötchen by the water on a sunny afternoon, and watch for the big ships, which announce themselves with a deep horn.