The stretch of Wall near Cawfields is where the whole thing makes the most sense, because the Romans used the landscape. Here the Great Whin Sill, a hard ridge of dark dolerite, rises in a line of crags along the north, and the Wall runs along the top of it, looking down over a drop on one side and a long slope on the other. Close to Cockmount Hill, the Wall and its southern ditch, the vallum, are both visible, and the milefortlet at Cawfields is one of the best preserved on the line, a square enclosure with a gateway still standing. Nearby, an old quarry has filled with water to make a small, dark lake at the foot of the crags.
The road that runs beside it, the B6318, is the Military Road, built after the Jacobite rising of 1745 so that troops could move across the country. General Wade's engineers laid it along the Wall, and in places they used the Wall's stones for the foundations, which is why long stretches of the Roman work have vanished. It is a splendid road for riding, with long straights, blind crests and bold bends, and it follows the ridge for miles. Wind is the main challenge, and the weather can turn from sun to rain in minutes. Sheep stray onto the road, so slow for the crests.
Haltwhistle, three and a half kilometres away, has the services you need, including fuel and a choice of cafes. Haydon Bridge, farther east, is much smaller, and Hexham, twenty-five kilometres off, is the nearest town of any size. The nearby fort of Great Chesters, known to the Romans as Aesica, was one of the main garrison posts in this central sector.
Pause on the crags and look both ways. To the north, the land falls away into empty moorland, once barbarian country, and to the south the green valley of the Tyne lies calm and farmed. It is easy to see why a frontier was drawn here, and equally easy to feel the loneliness of the men who patrolled it.