Hadrian's Wall (Latin: Vallum Aelium), also called the Roman Wall, Picts' Wall, or Vallum Hadriani, was a defensive fortification in the Roman province of Britannia, begun in AD 122 during the rule of emperor Hadrian. It ran between the River Tyne and the Solway Firth. It had a stone base and a stone wall. There were milecastles with two turrets in between. There was a fort about every five miles. From north to south the wall comprised a ditch, wall, military way and vallum (another ditch with adjoining mounds). The milecastles had static garrisons, whereas the forts had fighting garrisons of infantry and cavalry.