 The Roman Empire was among the most powerful economic, cultural, political and military forces in the world of its time, and it was one of the largest empires in world history.At its height under Trajan, it covered 5 million square kilometres.The Roman legacy has deeply influenced the Western civilisation, shaping most of the modern world; among the many legacies of Roman dominance are the widespread use of the Romance languages derived from Latin, the numerical system, the modern Western alphabet and calendar, and the emergence of Christianity as a major world religion.