Limestone Corner is the most northerly point on Hadrian's Wall, and it is famous for a job left unfinished. The Romans dug a defensive ditch in front of the Wall along most of its length, but here they hit a band of hard whinstone, and after cutting some of the huge blocks free and splitting others with wedges, they simply gave up. The blocks still lie where they were left, some with the holes for the wedges visible, nearly nineteen centuries later. Nearby, the earthworks of a Roman temporary camp, where troops on the move once pitched their tents behind a ditch and bank, are part of the same Frontiers of the Roman Empire World Heritage site.
The B6318, the Military Road, runs right past, and the corner is a good place to pull in and take a short walk along the ditch. The views from here stretch north over rough grazing and moorland towards the Cheviots and the Scottish border, and south over the Tyne valley. On a windy day, which is most days, you understand why the soldiers stationed here were not always keen on their posting.
Just to the east lies Chesters, one of the best-preserved Roman cavalry forts in Britain, with a bathhouse on the bank of the North Tyne. To the west, the Wall climbs towards the crags of the central section, with Housesteads and the great cliffs of the Whin Sill. Carrawburgh, a short way west of Limestone Corner, has the remains of a temple to Mithras, a mysterious Persian god popular with Roman soldiers, with replicas of its altars in place.
The riding here is a highlight of any trip in northern England. The Military Road is a roller-coaster of dips and crests, long straights and sudden bends, with constant views. It demands respect: the dips hide oncoming traffic, sheep wander onto the road, and in summer it is busy with tourists. Ride it early in the morning or in the evening, when the light is low and the road is quieter.
Hexham, about nine kilometres away, has fuel, shops, restaurants and a fine abbey church with a Saxon crypt built partly from Roman stones. Acomb and Chollerford are smaller villages with pubs. The George Hotel at Chollerford, beside the bridge over the North Tyne, is a well-known stop for walkers and riders.