A.D. 381 heretics, pagans, and the dawn of the monotheistic state ( PDFDrive )

Septimius Severus had rebuilt Byzantium after his capture of the old city.
Constantine appears to have left Severus’ foundation intact and constructed, just
outside its walls, an oval forum with a statue of himself in the guise of the sun
god, Helios, placed on a column in the centre. (The column still survives,
although in a very battered state.) Arched passageways led from the forum into
the Severan city and its main procession route, the Regia, and westwards along a
new processional route, the Mese (the Middle Street) to Constantine’s own set of
walls, which were situated 400 metres beyond those of Severus. Statues were
collected from all over the empire to embellish the ceremonial ways and the
forum. This was another tradition that, in Rome, had stretched back for many
centuries during which the booty of war had been brought back to the city in
triumph. Churches were also built, but their dedications to Wisdom (Sophia),
Peace (Eirene) and ‘the Sacred Power’ suggest that Constantine was working
with an imagery that was as much pagan as Christian. Certainly several pagan
temples were allowed to stand in the old city while only one church was
completed before Constantine’s death in 337: his mausoleum, the Church of the
Holy Apostles. Constantine was stressing the ancient tradition of the supreme
deity supporting the emperor - even if his own behaviour left it unclear whether
this was Jupiter (or Apollo), an abstract Platonic principle, Helios (or Sol
Invictus) or the Christian God. It was only after Constantine’s death that
Constantinople became an unambiguously Christian city. The city’s cult of the
ancient virgin goddess Rhea, left untouched by Constantine, gradually became
transformed into that of the Virgin Mary. 1 Constantinople soon acquired a
reputation for the passion and intensity with which its Christians discussed
theological issues.
The vast building programme and the designation of Constantinople as the
‘new Rome’ brought a large influx of immigrants. One estimate is that the
population already numbered some 90,000 by 340. The orator Libanius, whose
native Antioch was among those affected by the migration, complained that the
sweat of other cities was being transformed into the fat of the capital.
Constantinople had its own senate and its own consul, and Constantine set in
hand the building of a residential district of grand mansions so that the city’s
administrative elite could be suitably housed. Latin was the language of the
administration (and remained so until the sixth century), Greek that of the mass
of the population - an epistula from the emperor to an official would be sent out
in Latin and then translated into Greek if it was published by him. Settlement
was further encouraged by the grant of a permanent grain ration from Egypt.