Continuous Roman defensive barrier.
Begun by Hadrian in AD 122, the wall guarded the northwestern frontier of the province of Britain from barbarian (particularly Celtic) invaders. It extended 73 mi (118 km) from coast to coast, from Wallsend (Segedunum) to Bowness. It had towers, gates, and forts at regular intervals; a ditch fronted it and an earthwork (the vallum ) ran behind it. It was briefly abandoned in favour of the Antonine Wall , but it returned to use until с 410. Portions remain visible today.