Built on the orders of the Roman Emperor Hadrian and located in Great Britain, Hadrian’s Wall was a defensive fortification that marked the northwest frontier of the Roman Empire for three centuries. The wall measured 73 miles in length and stretched from coast to coast across present-day northern England, between Wallsend in the east to Bowness-on-Solway in the west. Construction likely started around A.D. 122, after Hadrian visited the Roman province then known as Britannia, and it’s thought to have taken an army of 15,000 men at least six years to complete it. The majority of the wall was made from stone, although some portions were fabricated from turf.

Small forts called milecastles were established at every Roman mile (the equivalent of .91 modern miles) along the wall, and two observation turrets were placed between each milecastle. Additionally, there were more than a dozen larger forts along the wall’s length where soldiers were stationed. An enormous earthwork consisting of a ditch flanked by parallel mounds, and now referred to as the Vallum, was created just south of the wall. Hadrian served as emperor from 117 until his death in 138. Afterward, the new emperor, Antoninus Pius, erected a turf wall to the north of Hadrian’s Wall, in present-day Scotland. However, the so-called Antonine Wall, which also had a number of forts along its length, was deserted in the 160s and the Romans reoccupied Hadrian’s Wall. The forts along the wall likely were occupied until the end of Roman rule in Britain, in the early 5th century.

In the ensuing centuries, stones from Hadrian’s Wall were removed to build homes and roads; however, portions of the wall still survive. Today, a long-distance walking path follows the wall’s route across northern England.