The Antonine Wall is a stone and turf fortification built across northern Great Britain by the Roman Empire in the middle 2nd century. The Roman emperor Antoninus Pius built the wall to control barbarians: the ancient Britons to the north of the wall, in Caledonia. The wall is now in Scotland, and runs between the Firth of Forth and the Firth of Clyde in the modern Scottish Lowlands. When the Romans built the wall, it was the northern border of the Roman Empire.