The place is said to have been colonized by Bottiaeans, and to have originally borne the name of Ancore (Steph. B. s. v.) or Helicore (Geogr. Min. p. 40, ed. Hudson); but it was subsequently destroyed by the Mysians. A few years after the death of Alexander the Great, Macedonian king Antigonus — who had taken control of much of Asia Minor upon the death of Alexander (under whom Antigonus had served as a general) — probably after his victory over Eumenes, in 316 BC, rebuilt the town, and called it, after himself, Antigoneia (Greek: Αντιγόνεια). (Steph. B. l. c.; Eustath. ad Horn. II. ii. 863) Several other of Alexander's generals (known together as the Diadochi (Latin; original Greek Διάδοχοι/Diadokhoi "successors")) later conspired to remove Antigonus, and after defeating him the area was given to Thessalian general Lysimachus (Lysimakhos) (circa 355 BC-281 BC) in 301 BC as his share of the lands. He renamed it Nicaea (Greek: Νίκαια, also transliterated as Nikaia or Nicæa; see also List of traditional Greek place names), in tribute to his wife Nicaea, a daughter of Antipater. (Steph. B., Eustath., Strab., ll. cc.) According to another account (Memnon, ap. Phot. Cod. 224. p. 233, ed. Bekker), Nicaea was founded by men from Nicaea near Thermopylae, who had served in the army of Alexander the Great. The town was built with great regularity, in the form of a square, measuring 16 stadia in circumference; it had four gates, and all its streets intersected one another at right angles, so that from a monument in the centre all the four gates could be seen. (Strabo xii. pp. 565 et seq.) This monument stood in the gymnasium, which was destroyed by fire, but was restored with increased magnificence by the younger Pliny (Epist. x. 48), when he was governor of Bithynia.
The city was built on an important crossroads between Galatia and Phrygia, and thus saw steady trade. Soon after the time of Lysimachus, Nicaea became a city of great importance, and the kings of Bithynia, whose era begins in 288 BC with Zipoetes, often resided at Nicaea. It has already been mentioned that in the time of Strabo it is called the metropolis of Bithynia, an honour which is also assigned to it on some coins, though in later times it was enjoyed by Nicomedia. The two cities, in fact, kept up a long and vehement dispute about the precedence, and the 38th oration of Dio Chrysostomus was expressly composed to settle the dispute. From this oration, it appears that Nicomedia alone had a right to the title of metropolis, but both were the first cities of the country.
The younger Pliny makes frequent mention of Nicaea and its public buildings, which he undertook to restore when governor of Bithynia. (Epist. x. 40, 48, etc.) It was the birthplace of the astronomer Hipparchus (ca. 194 BC), the mathematician and astronomer Sporus (ca. 240) and the historian Dio Cassius (ca. 165).[1] It was the death-place of the comedian Philistion. The numerous coins of Nicaea which still exist attest the interest taken in the city by the emperors, as well as its attachment to the rulers; many of them commemorate great festivals celebrated there in honour of gods and emperors, as Olympia, Isthmia, Dionysia, Pythia, Commodia, Severia, Philadelphia, etc. Throughout the imperial period, Nicaea remained an important town; for its situation was particularly favourable, being only 40 km (25 mi) distant from Prusa (Pliny v. 32), and 70 km (43 mi) from Constantinople. (It. Ant. p. 141.) When Constantinople became the capital of the Eastern Empire, Nicaea did not lose in importance; for its present walls, which were erected during the last period of the Empire, enclose a much greater space than that ascribed to the place in the time of Strabo. Much of the existing architecture and defensive works date to this time, early 300s.
Nicaea suffered much from earthquakes in 358, 362 and 368; after the last of which, it was restored by the emperor Valens. During the Middle Ages it was for a long time a strong bulwark of the Byzantine emperors against the Turks.
In the reign of Constantine, 325, the celebrated First Council of Nicaea was held there against the Arian heresy, and the prelates there defined more clearly the concept of the Trinity and drew up the Nicene Creed. The doctrine of the Trinity was finalized at the Council of Constantinople in 381 AD which expressly included the Holy Ghost as equal to the Father and the Son. The first Nicene Council was probably held in what would become the now ruined mosque of Orchan. The church of Hagia Sophia was built by Justinian I in the middle of the city in the 6th century (modelled after the larger Hagia Sophia in Constantinople), and it was there that the Second Council of Nicaea met in 787 to discuss the issues of iconography.