The Roman Empire was the largest and most enduring of the ancient world. From its zenith under Augustus and Trajan in the first century AD to its decline and fall amidst the barbarian invasions of the fifth century, the Empire guarded and maintained a frontier that stretched for 5,000 kilometres, from Carlisle to Cologne, from Augsburg to Antioch, and from Aswan to the Atlantic. Far from being at the periphery of the Roman world, the frontier played a crucial role in making and breaking emperors, creating vibrant and astonishingly diverse societies along its course which pulsed with energy while the centre became enfeebled and sluggish. This remarkable new book traces the course of those frontiers, visiting all its astonishing sites. Philip Parker reveals how and why the Empire endured for so long, as well as describing the rich and complex architectural and cultural legacy which it has bequeathed to us.