Epiacum Roman fort, Northumberland: Under the yarrow and sheep’s sorrel of the short turf were the gates, towers and bath house of the stone-built fort Hill cloud rolls over the fell top where snow still fills the cups and hollows of high ground. I’m walking a section of the Pennine Way near Alston, uplifted by the layers of overlapping sound: curlews bubbling, peewits wing-thrumming, skylarks trilling. The path drops steeply down to the Gilderdale Burn, the county boundary between Cumbria and Northumberland. Climbing up again, the ground is spongy with recent rain, wet seeping into my boots. A series of grassy mounds and banks stand lime-green vivid against a lowering sky. Tiered like contemporary landform art, they were made nearly 2,000 years ago. This is Epiacum Roman fort on Castle Nook farm, and it has some of the best preserved earthworks of Roman Britain. Built about the same time as Hadrian’s Wall to the north, it is on the line of the Maiden Way that marched up to Carvora...