The Roman eastern frontier stretched from the north-east shore of the Black Sea to the Red Sea. It faced Rome's formidable foe, the kingdom of Parthia, and its successor, Sasanian Persia. Rome's bulwark in antiquity was the area known as Syria or the Levant, roughly modern Syria, Lebanon, Jordan, Israel and Palestine. To the south lay the Nabataean kingdom, annexed by Rome in 106 and formed into the province of Arabia. To the north, the Cappadocian frontier was laid out in one of the most inaccessible and remote parts of Eurasia facing extremes of climate and topography, amid a patchwork of client kingdoms. This hidden and fascinating frontier in Turkey, whose bases mostly lie under reservoirs, is the major omission from this volume and it is hoped that a more in-depth account might appear in due course. The Caucasian forts along the edge of the Black Sea are, however, part of this volume; this is perhaps Rome's least known frontier archaeologically but the subject of a unique account by Arrian when governor of Cappadocia.