Few people expect to find a Roman frontier running through a spa town, but the Limes did cross the Lahn near Bad Ems, and the stretch around the Lahn valley is one of the most scenic parts of its whole length. At this point, watchtower WP 1/88 a stands in the hills above Dausenau, a village of a few hundred houses on the river, a couple of kilometres from the spot. The frontier ran along the heights and dropped to the water, and the Romans controlled the river crossing from both sides.
Dausenau itself is delightful, with half-timbered houses, a medieval town wall with towers, and a church whose tower leans at an alarming angle, a result of soft ground and ageing timber. Bad Ems, a short ride downstream, was a fashionable spa in the nineteenth century, a favourite of Russian tsars and German kings. It is also the place where in 1870 a telegram known as the Ems Dispatch was edited by Bismarck in a way that helped to push France and Prussia into war. The grand spa buildings and the long promenade by the river give the town a faded elegance.
The Lahn valley is a wooded, winding river canyon, with steep slopes, vineyards in places, and ruined castles on the heights. The Limes is part of the UNESCO listing of 2005, and you can follow marked trails that lead to the towers and earthworks. The hills are covered in oak and beech, and in the evening, the light turns warm.
The roads along the Lahn and over the hills are fun for riders, with plenty of bends and good views, though they can be crowded with cyclists, walkers and caravans in summer. Surfaces are good, and there are several small bridges and narrow village streets, so slow down. Fuel is available at Bad Ems, with a few supermarkets, bakeries and restaurants, and rooms are easier to find midweek. Spring and autumn are the most pleasant times, and early on a clear morning, the air in the valley is wonderful.