Vallum Hadriani (Hadrian’s wall), c. 122 CE

A map illustrating the span, structure, and context of the 73 miles (118 km) Hadrian’s Wall (also called the Vallum Aelii, Aelius being the family name of emperor Hadrian). Built by a force of more than 15,000 soldiers from the three roman legions stationed in Britain, with an intent “to separate the Romans from the barbarians” (the Picts and other tribes to the north of Britain), the wall defined the northern frontier of the Roman Empire along the Tyne–Solway isthmus and created a military zone full of forts, milecastles, ramparts, roads, barracks and bustling settlements from the North Sea to the Irish Sea.