Hadrian's Wall

Hadrian's Wall, ancient Roman defensive wall in northern Britain that originally ran 117 km (73 mi) from the Solway Firth in the west to the mouth of the River Tyne in the east. Its purpose was to protect the northern boundary of Roman Britain against hostile Pictish tribes. It also marked the frontier of Roman civil jurisdiction.

Emperor Hadrian ordered its construction in about ad 122. The wall was still being modified when he died in ad 138. The section west of the River Irthing was originally made of turf but was replaced by stone; near Birdoswald, the turf and stone walls follow different courses. The wall, built entirely in stone in its final form, was 2.4 to 3 m (8 to 10 ft) thick and probably 3.6 to 4.8 m (12 to 16 ft) high. The wall was patrolled by mile castles built one Roman mile (1,714 m/1,875 yd) apart, with two smaller observation turrets or towers placed regularly between each pair. Forts capable of holding 10,000 men were built at intervals of about 11 km (7 mi) along its length, and a military road ran along its south side. A ditch was dug along the north side of the wall, except where crags gave natural protection. Hadrian's Wall was overrun by the Picts three times (in the ad 180s, 297, and 367) and was finally abandoned in about 400. Sections of the wall still stand today. In 1987, the monument was designated a UNESCO World Heritage Site.