The emperor Trajan, who reigned between A.D. 98 and A.D. 117, was not only a great conqueror, carrying the Roman armies beyond the Danube into Dacia, and into Armenia, Mesopotamia, and Assyria, and thus extending and rendering more accurate the geographical knowledge of his subjects; but he was also attentive to the improvement and commercial prosperity of the empire. He made good roads from one end of the empire to the other; he constructed a convenient and safe harbour at Centum Cellæ (Civita Vecchia), and another at Ancona on the Adriatic: he dug a new and navigable canal, which conveyed the waters of the Nahar-Malcha, or royal canal of Nebuchadnezzar, into the river Tigris; and he is supposed to have repaired or renewed the Egyptian canal between the Nile and the Red Sea. He also gave directions and authority to Pliny, who was appointed governor of Pontus and Bithynia, to examine minutely into the commerce of those provinces, and into the revenues derived from it, and other sources. The emperor Adrian passed nearly the whole of his reign in visiting the different parts of his dominions: he began his journey in Gaul, and thence into Germany; he afterwards passed into Britain. On his return to Gaul, he visited Spain; on his next journey he went to Athens, and thence into the east; and on his second return to Rome, he visited Sicily; his third journey comprised the African provinces; his fourth was employed in again visiting the east; from Syria he went into Arabia, and thence into Egypt, where he repaired and adorned the city of Alexandria, restoring to the inhabitants their former privileges, and encouraging their commerce. On his journey back to Rome, he visited Syria, Thrace, Macedonia, and Athens. By his orders, an artificial port was constructed at Trebizond on a coast destitute by nature of secure harbours, from which this city derived great wealth and splendour.