Where does the Wall go when it reaches a city? In Carlisle, it takes a quiet route under the pavement. The Roman fort of Luguvalium stood here, on the south bank of the River Eden, to guard a crossing, and the line of the frontier ran north of the town, through what is now the suburb of Stanwix. Along the road between Houghton Road and the river, you are following a stretch where the Wall once stood, though you would need a map and a good imagination to see it. A small plaque, a piece of ditch or a slightly raised bank is all that remains.
Building began in AD 122, in the time of the governor Aulus Platorius Nepos, and the western section, which includes this stretch, was at first made of turf rather than stone. It was later rebuilt in stone, and the whole thing ran for eighty Roman miles, from the Tyne to the Solway. It was not a barrier in the sense of a Berlin Wall, since soldiers could march through the gates, but it controlled movement and marked the edge of the empire. Today it is part of the Frontiers of the Roman Empire World Heritage Site.
The riding here is a modest thing. The road into Carlisle from the north runs through hedged farmland and low hills, then joins streets of brick houses and shops, with traffic lights and roundabouts. Surfaces are good and speeds are low. At the northern edge, you can turn onto quiet country lanes, where the light is soft and the fields are full of sheep. At the end of the day, a visit to the Tullie House museum in the centre of the city explains the Roman story, with finds from forts all along the Wall, including leather shoes and writing tablets.
The Parton Roman fort, which sits on the west coast of Cumbria, was part of a chain of coastal defences that continued the Wall's idea south along the sea. It is another site where the evidence lies under the ground.
Fuel is plentiful in Carlisle, and the cafes near the station are good. Wind and rain are the norm, so pack your waterproofs. The end of spring and September offer the best weather.