The Nord-Ostsee-Kanal — the Kiel Canal — connects the North Sea to the Baltic at its eastern end in Kiel, and is the world's busiest artificial waterway by vessel count. Some 30,000 ships pass through each year, cutting 460km off the voyage around the Jutland peninsula.
The Holtenau locks at the canal's eastern entrance are the place to see it. Ships the size of city blocks glide through a gap barely wider than their beam, within metres of the towpaths and benches where visitors sit. The contrast between the suburban setting and the industrial scale of the vessels is startling.
The canal itself stretches west across Schleswig-Holstein to Brunsbüttel on the Elbe. Cycle paths run along much of its length, and there are viewing benches at several bridges along the route for those who want more ship-watching.