| Around ad 122, Roman Emperor Hadrian ordered the construction of a wall in northern Britain, then part of the Roman Empire, to keep out the unconquered Caledonians of Scotland. Built out of stone and turf and measuring about 117 km (73 mi) in length, the wall linked a series of forts and watchtowers. The Romans rebuilt Hadrian’s Wall several times throughout the 200s and 300s and used it as a fortification until about 400. |