an ancient city of Thrace, situated on the Bosphorus. It was founded, according to Eusebius, about the thirtieth Olympiad, when Tullus Hostilius reigned in Rome. But, according to Diodorus Siculus, the foundations of this metropolis were laid in the time of the Argonauts, by one Byzas, who then reigned in the neighbouring country, and from whom the city was called Byzantium. This Byzas, according to Eustathius, arrived in Thrace a little before the Argonauts came into those seas, and settled there with a colony of Megarenses. But Velleius Paterculus ascribes the founding of Byzantium to the Milesians, while Ammianus Marcellinus attributes it to the inhabitants of Attica. Some ancient medals of Byzantium, however, bear the name and head of Byzas, with the prow of a ship on the obverse. The year after the destruction of Jerusalem by Titus, Byzantium was reduced into the form of a Roman province. In A.D. 193 the city took part with Niger against Severus, and was strongly garrisoned by Niger, as being a place of the utmost importance. But it was soon afterwards invested by Severus; and as he was universally hated on account of his cruelty, the inhabitants defended themselves with the greatest resolution. Having been supplied with a great number of warlike machines, most of them invented and built by Periscus, a native of Nicaea, and the greatest engineer of his age, they for a long time baffled all the attempts of the assailants, killed great numbers of them, crushed such as approached the walls with large stones; and when stones began to fail, they discharged the statues of their gods and heroes as missiles against the enemy. But at last they were obliged to submit, through famine, after having been reduced to the necessity of devouring one another. The conqueror put all the magistrates and soldiers to the sword; but he spared the engineer Periscus.

Before this siege Byzantium was the greatest, wealthiest, and most populous city of Thrace. It was surrounded by walls of an extraordinary height and breadth, defended by a great number of towers, seven of which were built with such art that the least noise heard in one of them was immediately conveyed to all the rest. Severus, however, no sooner became master of the place, than he commanded it to be laid in ashes. The inhabitants were stripped of all their effects, and publicly sold as slaves, whilst the walls were levelled with the ground. But from the chronicle of Alexandria we learn, that soon after this terrible catastrophe Severus himself caused a great part of the city to be rebuilt, calling it Antonia, after his son Caracalla, who assumed the surname of Antoninus. In A.D. 262, the tyrant Galienus wreaked his fury on the inhabitants of Byzantium. He intended to besiege it, but on his arrival despaired of being able to make himself master of so strong a place. He was, however, admitted next day into the city; and, without any regard to the terms agreed on, he caused the soldiers and all the inhabitants to be put to the sword. Trebellius Pollio says, that not a single person was left alive. What reason there was for such an extraordinary massacre we are nowhere informed. In the wars between the Emperors Licinius and Maximin the city of Byzantium was obliged to submit to the latter, but it was soon afterwards recovered by Licinius. In the year 323, it was taken from Licinius by Constantine the Great, who in 330 enlarged and beautified it, with a design to make it the second, if not the first city in the Roman empire. He began with extending the walls of the ancient city from sea to sea; and whilst some of the workmen were busied in rearing these defences, others were employed in raising within them a great number of stately buildings, amongst which was a palace nowise inferior in extent and magnificence to that of Rome. He built a capital and an amphitheatre, and constructed a circus maximus, several forums, porticoes, and public baths. He divided the whole city into fourteen regions or wards, and granted the inhabitants many privileges and immunities. By these means Byzantium became one of the most flourishing and populous cities of the empire. Vast numbers of people flocked thither from Pontus, Thrace, and Asia, as Constantine, by a law enacted A.D. 330, had decreed that no person who had lands in those countries should be at liberty to dispose of them, or even to leave them to his proper heir at his death, unless such heir had a house in the new city. But however desirous the emperor might be that his city should be filled with people, he did not care that it should be inhabited by any but Christians. He therefore caused the idols to be pulled down, and the temples to be consecrated to the true God. Besides, he built an incredible number of churches, and caused crosses to be erected in all the squares and public places. When most of the buildings were finished, he caused the city to be solemnly dedicated to the Virgin Mary, according to Cedrenus, but according to Eusebius, to the God of Martyrs. At the same time Byzantium was declared equal in rank to Rome; and similar rights, immunities, and privileges were granted to its inhabitants, with those enjoyed by the metropolis. Constantine established a senate and other magistrates, with power and authority equal to those of old Rome; and he took up his residence in the new city, changing its name to Constantinople.