Arzbach sits a few kilometres north of the Lahn, in the wooded Westerwald hills behind Bad Ems, and it is one of those places where the Roman Empire left a mark you have to squint to see. The fort and its civil settlement belonged to the Upper German-Raetian frontier, the Limes, which ran for hundreds of kilometres from the Rhine near Rheinbrohl all the way to the Danube. Here it was a ditch, a rampart and a timber palisade, studded with watchtowers within sight of one another. Nothing grand survives above ground in the village itself. What you get is the lie of the land: a ridge chosen because a sentry could see from it, and a settlement that grew beside the soldiers because soldiers need bread, boots and beer.
The riding is the reason to link it with the rest of the Limes sections. Roads here are the quiet kind that Rhineland-Palatinate does so well, narrow ribbons through beech and spruce, with tight little bends where a stream has cut a fold into the slope, and then a short open stretch over farmland where you can see the next ridge. Surfaces are generally decent, though forestry trucks leave mud and gravel at junctions, and leaves lie thick in autumn. Mornings are best, before the Sunday walkers appear at the car parks.
The nearest proper town is Bad Ems, about five kilometres away, a nineteenth-century spa on the Lahn. It is where the famous telegram of 1870 was drafted that helped tip France and Prussia into war, and where Kaiser Wilhelm took the waters. It has fuel, cafes along the river and a handful of grand, faintly faded bathing halls.
This is also the gateway to the Limes the way many riders meet it, a series of numbered watchtower positions marked by small signs, a reconstruction here, a low mound there. The mood is pastoral, slightly eerie, and quiet enough that you can hear the engine tick as it cools. If you like places where you have to supply the imagination, stop, turn the engine off, and look along the ridge line the way a legionary would have.