The Antonine Wall, known to the Romans as Vallum Antonini, was a turf fortification on stone foundations, built by the Romans across what is now the Central Belt of Scotland, between the Firth of Forth and the Firth of Clyde. Representing the northernmost frontier barrier of the Roman Empire, it spanned approximately 63 kilometres (39 miles) and was about 3 metres (10 feet) high and 5 metres (16 feet) wide. Security was bolstered by a deep ditch on the northern side. It is thought that there was a wooden palisade on top of the turf. The barrier was the second of two "great walls" created by the Romans in Northern Britain. Its ruins are less evident than the better-known Hadrian's Wall to the south, primarily because the turf and wood wall has largely weathered away, unlike its stone-built southern predecessor.
Construction began in AD 142 at the order of Roman Emperor Antoninus Pius, and took about 12 years to complete. Antoninus Pius never visited Britain, whereas his predecessor Hadrian did. Pressure from the Caledonians may have led Antoninus to send the empire's troops further north. The Antonine Wall was protected by 16 forts with small fortlets between them; troop movement was facilitated by a road linking all the sites known as the Military Way. The soldiers who built the wall commemorated the construction and their struggles with the Caledonians in decorative slabs, twenty of which still survive. The wall was abandoned only eight years after completion, and the garrisons relocated back to Hadrian's Wall. In 208 Emperor Septimius Severus re-established legions at the wall and ordered repairs; this has led to the wall being referred to as the Severan Wall. The occupation ended a few years later, and the wall was never fortified again. Most of the wall and its associated fortifications have been destroyed over time, but some remains are still visible. Many of these have come under the care of Historic Scotland and the UNESCO World Heritage Committee.