In Decline and Fall of the Roman Empire, Volume 1, Chapter XVII, Foundation of Constantinople Gibbon starts with a wonderful description of Constantinople – the former Byzantium – and its environs. As usual, this is accompanied by ample footnotes, which are available in this online version to. The description begins thus:
If we survey Byzantium in the extent which it acquired with the august name of Constantinople, the figure of the Imperial city may be represented under that of an unequal triangle. The obtuse point, which advances towards the east and the shores of Asia, meets and repels the waves of the Thracian Bosphorus. The northern side of the city is bounded by the harbour, and the southern is washed by the Propontis or Sea of Marmora. The basis of the triangle is opposed to the west, and terminates the continent of Europe. But the admirable form and division of the circumjacent land and water cannot, without a more ample explanation, be clearly or sufficiently understood…
According to legend, Byzantium was founded by Byzas, however:
BYZAS (Bu£"as), a son of Poseidon and Ceroessa, the daughter of Zeus and Io. He was believed to be the founder of Byzantium. (Steph. Byz. s. v.; Diod. iv. 49.) This transplantation of the legend of Io to Byzantium suggests the idea, that colonists from Argos settled there. The leader of the Megarians, who founded Byzantium in b. c. 658, was likewise called Byzas. Dictionary of Greek and Roman Biography and Mythology, page 520 (v. 1).
Courtesy David Meadows of rogueclassicism, here is brief history of Istanbul beginning with the Megarians. (Turkish Daily News)
Strabo in his Geography refers to Byzantium in Book II Chapter 1 and Book VII, Chapter 6.
More on the history of Byzantium/Constantinople can be found in this online chapter of Cyril Mango, Byzantium: The Empire of New Rome.
In print Byzantium: The Empire of the New Rome.
Cyril Mango has also edited The Oxford History of Byzantium. There is a paperback version too. (no image available)
The image of Constantine, c. 1000 AD, on top of the post is from a mosaic in the Hagia Sophia, showing the emporer with a model of the city.
Wikipedia has a nice map of Byzantine Constantinople. There is second version: detailed map. The latter may be useful for our chats on December 6 & 13 (Bearkeeper's Daughter & Imperial Purple).
Online book chat on Gibbon, November 15.