The wall's construction started in 122 AD under Emperor Hadrian, who wanted to protect the Roman Empire's northern frontier against raids by the Picts and other tribes. The wall bisected the province of Britannia from the Scottish lowlands of Caledonia.
Although attempts to conquer more of Scotland followed the construction of the border, Hadrian's Wall marked the northern boundary of the Empire for hundreds of years. The wall connected the east and west coasts of Britain, a remarkable feat even for the Romans.
It took three full legions – some 15,000 men – a total of six years to build the majority of Hadrian's Wall. A network of fortifications was also constructed along the length of the wall, consisting of turrets, milecastles, and larger forts. These garrisons contained almost 10,000 men at full strength.
Larger fortifications were established at key strategic points, with smaller milecastle forts positioned at every Roman mile (about 1600 yards or just under 1500 meters). Each milecastle was flanked by two turrets, which stood at a distance of about 540 yards or 495 meters on either side. In total, the wall supported around 80 milecastles and nearly 160 turrets.