The Antonine Wall, the northernmost boundary of the Roman Empire, is located in what country?

The Antonine Wall, known to the Romans as "Vallum Antonini", was a turf fortification on stone foundations, built by the Romans extending about 36.5 miles (58.5 km) across Scotland between the River Clyde and the Firth of Forth. It was built around AD 142 on the orders of the emperor Antoninus Pius by the Roman army under the command of the governor Quintus Lollius Urbicus.

The wall was of turf on a stone base 15 Roman feet (4.44 m) wide and stood perhaps 10 feet (3 m) high; in front was a ditch up to 40 feet (12 m) wide and 12 feet (4 m) deep; a wide, shallow mound was formed on the ditch’s north side when the material was tipped out. Sixteen forts—built in two stages—are known along the wall, and fortlets lay between many of these. All were connected by a road, the Military Way. An aerial survey has revealed 20 camps used by the soldiers who built the wall.

Legionaries who constructed the wall recorded their work in a spectacular series of “distance slabs.” These slabs not only recorded the lengths of the wall sections, with measurements sometimes as precise as to the nearest foot but also depicted in friezes aspects of the campaign against the “northern barbarians". Seventeen of the 20 known slabs are in the Hunterian Museum at Glasgow University, under the care of Historic Environment Scotland and the UNESCO World Heritage Committee.

The wall was abandoned only eight years after completion, around AD 160, and the army returned to Hadrian’s Wall.