Though Rome was never completely able to conquer Caledonia, the Roman general Gnaeus Julius Agricola invaded the highlands in the first century A.D., and conquered the border region as far north as the Firth of Forth. As a defense against the Picts, in 122 A.D. the Emperor Hadrian built a rampart from the Firth of Solway to the mouth of the Tyne River, known as "Hadrian's Wall."