The Danevirke is a monument you walk along more than you look at, and the Arched Wall is a good place to see why. The rampart here bends in a long gentle curve across the fields, a green bank with a ditch beside it, and from the top you can follow its shape to the horizon. The line has the odd, deliberate look of something designed by people who understood the ground: it skirts a wet hollow here, climbs a low rise there, and always keeps the high side on the Danish side.
History crowded round this place more than once, but the most recent chapter was in February 1864. The Second Schleswig War was only weeks old, and the Danish army was dug in along the Danevirke, expecting a Prussian and Austrian assault. A hard frost made the marshes passable and threatened to let the enemy go around the flank, so on the night of the fifth to the sixth, the Danes quietly abandoned the line and marched north. It was a sensible decision and a national humiliation. Within two months the Prussians stormed the Danish positions at Dybbøl, and the duchies of Schleswig and Holstein were lost to Denmark for more than half a century.
The riding is mild and the countryside is simple, with the roads running between fields of grain and rape and crossing the line at gentle angles. Dannewerk, with a thousand inhabitants, lies a couple of kilometres off, and Schuby is a little further. Tractors are the main obstruction, and cyclists the main company. In summer the verges are bright with poppies and cornflowers, and the sound of skylarks drifts down from the sky.
The nearest town of any size is Schleswig, four kilometres away, with fuel, supermarkets and cafés. Park at one of the signposted points and walk along the bank, which is open to the public. Be careful where the ground drops into the ditch, and avoid trampling crops. The wall is a quiet, rather moving thing, and the best way to take it in is slowly, with the wind in your face and an open sky.