Byzantium, renamed Constantinople.
324 written in roman numeral is CCCXXIV
"He decided on the ancient Greek city of Byzantium. And on 8 November AD 324 Constantine created his new capital there, renaming it Constantinopolis (City of Constantine). He was careful to maintain Rome's ancient privileges, and the new senate founded in Constantinople was of a lower rank, but he clearly intended it to be the new center of the Roman world."So Constantinopolis would be your answer.Source: http://www.roman-empire.net/decline/constantine-index.html
ConstantineConstantinopolos, founded 324 and dedicated 11 May 330. Known as Constantinople in English and served as the Imperial capital for 16 centuries
Constantine was an Emperor of Rome who stopped the persecution of Christians and in 324 made Christianity the official religion of the Roman Empire. Then in 330 he moved his capital from Rome to Byzantium and renamed it Constantinople.
Initially, it was Rome. The capital was moved by Emperor Constantine to Constantople (modern Istanbul) for strategic reasons: it was more easily defended. He named it Nova Roma; it was named after Constantine following his death.
CCCXXIV
324
Unfortunately there's not a clear answer to this as historians disagree over when the 'Byzantine Empire' changed from simply being the 'Roman Empire'. In truth, the populace of the empire never considered themselves to be 'Byzantine', they actually thought of themselves as Roman. 'Byzantium', as it is referred to today, is a bit of an awkward term that was created by pre-twentieth century historians. It's used to describe the late Roman Empire and comes from the original name of its capital city: Constantinople. Which had previously been known as 'Byzantium'. There are a group of arguments amongst historians with regards to when 'Byzantium' began:In 286 AD when the Roman Empire was divided into Eastern and Western halves by the Emperor Diocletian.When Constantine built the city of Constantinople, c.324-330 ADWhen the last Western Roman Emperor died, 476 ADDuring the Islamic expansion in the 7th century ADThough there is an agreed upon end-date(1453). In truth it may simply be easier to view this as the 'Later Roman Empire', as many of the customs and traditions (though certainly not the religious commitments) of the people stay the same until the Islamic expansions - hence the argument for such being the beginning of 'Byzantium'.
Constantinople was originally named Byzantium by the Greeks who founded a colony there in the 7th century BCE. It was renamed Konstantinoupolis (Constantinople) after Constantine I in 324 CE; Constantine transferred the capital of the Roman Empire from Rome to Constantinople in 330 CE. Constantinople's modern name, Istanbul, comes from the Greek phrase 'eis tin polin' which means 'into the City.' After the Republic of Turkey was created in 1923, the Turkish government began to officially reject the use of Constantinople as an acceptable name for Istanbul.
CCCXX1V
"He decided on the ancient Greek city of Byzantium. And on 8 November AD 324 Constantine created his new capital there, renaming it Constantinopolis (City of Constantine). He was careful to maintain Rome's ancient privileges, and the new senate founded in Constantinople was of a lower rank, but he clearly intended it to be the new center of the Roman world."So Constantinopolis would be your answer.Source: http://www.roman-empire.net/decline/constantine-index.html