It was an ancient tradition that, when the Capitol was founded by one of the Roman kings, the god Terminus (who presided over boundaries, and was represented according to the fashion of that age by a large stone) alone, among all the inferior deities, refused to yield his place to Jupiter himself. A favourable inference was drawn from his obstinacy, which was interpreted by the augurs as a sure presage that the boundaries of the Roman power would never recede. During many ages, the prediction, as it is usual, contributed to its own accomplishment. But though Terminus had resisted the majesty of Jupiter, he submitted to the authority of the emperor Hadrian. The resignation of all the eastern conquests of Trajan was the first measure of his reign. He restored to the Parthians the election of an independent sovereign; withdrew the Roman garrisons from the provinces of Armenia, Mesopotamia, and Assyria; and, in compliance with the precepts of Augustus, once more established the Euphrates as the frontier of the empire. Censure, which arraigns the public actions and the private motives of princes, has ascribed to envy a conduct which might be attributed to the prudence and moderation of Hadrian. The various character of that emperor, capable, by turns, of the meanest and the most generous sentiments, may afford some colour to the suspicion. It was, however, scarcely in his power to place the superiority of his predecessor in a more conspicuous light, than by thus confessing himself unequal to the task of defending the conquests of Trajan.
The martial and ambitious spirit of Trajan formed a very singular contrast with the moderation of his successor. The restless activity of Hadrian was not less remarkable when compared with the gentle repose of Antoninus Pius. The life of the former was almost a perpetual journey; and as he possessed the various talents of the soldier, the statesman, and the scholar, he gratified his curiosity in the discharge of his duty. Careless of the difference of seasons and of climates, he marched on foot, and bareheaded, over the snows of Caledonia, and the sultry plains of the Upper Egypt; nor was there a province of the empire which, in the course of his reign, was not honoured with the presence of the monarch. But the tranquil life of Antoninus Pius was spent in the bosom of Italy; and, during the twenty-three years that he directed the public administration, the longest journeys of that amiable prince extended no farther than from his palace in Rome to the retirement of his Lanuvian villa.
Under his reign, as has been already mentioned,  the empire flourished in peace and prosperity. He encouraged the arts, reformed the laws, asserted military discipline, and visited all his provinces in person. His vast and active genius was equally suited to the most enlarged views and the minute details of civil policy. But the ruling passions of his soul were curiosity and vanity. As they prevailed, and as they were attracted by different objects, Hadrian was, by turns, an excellent prince, a ridiculous sophist, and a jealous tyrant. The general tenor of his conduct deserved praise for its equity and moderation. Yet, in the first days of his reign, he put to death four consular senators, his personal enemies, and men who had been judged worthy of empire; and the tediousness of a painful illness rendered him, at last, peevish and cruel. The senate doubted whether they should pronounce him a god or a tyrant; and the honours decreed to his memory were granted to the prayers of the pious Antoninus.
- Gibbon, Edward, and Hugh Trevor-Roper. The Decline and Fall of the Roman Empire. New York: Alfred A. Knopf, 1993. Print. 10-11, 87.