Dan Snow explores the physical remains of Hadrian’s vast project of 122AD - over 80 Roman miles of wall, turrets and forts, stretching from coast to coast across northern England. Mile after mile of stone marching over the horizon. Dan meets leading experts along the Wall and visits some of the key sites - from Arbeia in the east (where tombstones reveal people here from as far away as Syria) to Birdoswald in the west (where a blatant carving of a phallic symbol shows the Wall was more than just