Hadrian's wall was commissioned by Emperor Hadrian in 122 AD in order to solidify Rome's claim to southern Britain and discourage Scottish attacks. With a workforce over fifteen thousand strong, it took six years to build the 117 km wall which bisected Northern Britain from the River Tyne in the west to the Solway Firth in the east. Its width and height varied from three to six meters and three to five metres, respectively.
Each of the three legions who worked on Hadrian's Wall (the second, the sixth and the twentieth) was divided into equal groups, each of which had responsibility over one 8 km segment of the wall. Small milecastles were built every one Roman mile (1.47 km) with two turrets evenly spaced between them. Larger forts were built every five miles (7 km), with small towns (vicus) usually supporting them.