The Romans were obsessed with water, and even on this bleak ridge they went to extraordinary trouble to bring it to their fort. The fort of Great Chesters, called Aesica in Roman times, stood on a crag high above the Haltwhistle Burn, with no spring close enough to supply a garrison of several hundred men and their animals. So the engineers built an aqueduct, an open channel that ran for about eight kilometres, following the contours of the land from a stream to the west, and delivered a steady flow into the fort. It was no great arched structure with spans of stone, but a simple ditch, and its beauty lies in the precision of the gradient. You can still trace the channel as a shallow line in the grass.
The country is high, open and often empty. A short ride from Haltwhistle brings you onto the ridge, where the Military Road runs in long straights across the moor, with sudden dips and crests and the occasional blind bend. Sheep graze the verges and sometimes the road, and the wind sweeps unimpeded. In clear weather the view stretches for miles across Northumberland, and in poor weather the cloud comes down, and the place feels austere.
Haltwhistle, four kilometres away, has fuel, food and shelter, and it is a pleasant market town with old stone houses. Haydon Bridge is much smaller, and Hexham is more than twenty kilometres off. At Chesterholm, to the east, the Vindolanda fort has yielded an extraordinary collection of wooden writing tablets, including a woman's invitation to a birthday party and a soldier's request for more socks and underpants, which bring the garrison to life in a very human way.
Walk out and look for the channel. It takes a moment to see, but once you do, the engineering begins to emerge. The Roman Army was not just a fighting force, it was an organisation of surveyors and builders. Out here in the wind, you can sense how much effort went into keeping a few hundred soldiers supplied with something as ordinary as water.