The north-eastern frontier of the Roman Empire - one of the great gaps in modern knowledge of the ancient world - has long eluded research. It has defied systematic exploration and been insulated against all but passing survey by wars, instability, political sensitivities, language, and the region's wild, remote mountains, mostly accessible only on horseback or on foot. Its path lay across eastern Turkey, following the Euphrates valley northwards from Syria, through gorges and across great ranges, and passing over the Pontic Alps to reach the further shores of the Black Sea. Vespasian established Rome's frontier against Armenia half a century before Hadrian's Wall. Five times as long, and climbing seven times as high, it was garrisoned ultimately by four legions and a large auxiliary army, stationed in intermediate forts linked by military roads. The two volumes of - based on research, field work conducted largely on foot, and new discoveries - document the topography, monuments, inscriptions, and sighted coins of the frontier, looking in detail at strategic roads, bridges, forts, watch and signalling systems, and navigation of the Euphrates itself. Study of the terrain provides a foundation for interpreting the literary and epigraphic evidence for the frontier and its garrisons. Military activity, which extended to the Caucasus and the Caspian, is placed in the context of climate, geography, and inter-regional trade routes. 28 colour maps and over 350 photographs, plans, and travellers' sketches not only document the history of eastern Turkey as a frontier region of the Roman empire, but also reveal an ancient way of life, still preserved during the 1960s and 1970s, but now almost obliterated by the developments of the modern world.