Born in Niš on February 22nd, 275 or 280 AD, of the father Constantine Chlorus (paleface) - Marcus Flavius Valerius Constantinus "Chlorus", and the mother Helen (Helena), an innkeeper's daughter, he was given the name Caius Flavius Valerius Aurelius Claudius Constantinus, named the Saint Czar Constantine afterwards. When he was seventeen, he was separated from his mother because of her humble extraction, at the insistence of his father. Having been deserted, Helen (St. Czarina Helena) devoted herself to the service of Christ. Although she was detached from her son, deprived of his parental home, she had undoubtedly influenced his personality development. The morality of Constantine is best reflected in his respect shown to the tradition of the empire he had headed from the year 306, having had the visionary knowledge that it was being overcome by a new culture. For this very reason, in spite of being known as a Christian, he would get baptized by an Arian shortly before his death, for Easter 337. He died in Nicomedia on May 22nd, 337.
During his lifetime, Saint Czar Constantine contributed greatly to the Christianity. After having had the Vision in 312, he started honoring the one Supreme God, as he had always been emphasizing. On the eve of a battle against much superior Maxentius, while crossing the Alps and entering Italy, full of distress on his horse back, he saw a cross of light in the heavens bearing the inscription: "En touto nica" (conquer by this). The troops behind him witnessed the same miracle. The nightfall found him amazed and concerned. In his dream, the Savior appeared to him with the same heavenly sign and commanded him to put it on his battle colors. The next morning he ordered his army to do so. The first banner with the cross is known under the name Labarum. Constantine placed the Monogram of Christ on his helmet, while his soldiers had it on their shields. Encouraged by the God, he defeated Maxentius (who drowned in the Tiber on October 29th, 312) and entered Rome victoriously. Since that moment, he had openly confessed his belief in the Supreme God.
In the year 313, he promulgated the Edict of Milan. The Edict granted Christians the freedom to practice their faith, thus equalizing the Christianity with all the other cults. He acknowledged the Christian church and gave it legal rights to public religious service, organization and action, while the clergy were awarded certain privileges (they did not serve the military obligation, paid no taxes, etc.). It brought about the division of power into secular and church authorities. This had a particular reflection in the church architecture, and numerous archeological sites in Niš bear witness to it. Classical writers are emphasizing in the Emperor's biography that: "Niš was the birthplace of Constantine the Great, who had later decorated this town magnificently" - Hic iqitur Constantinus natus... in oppido Naisso atque eductus, quid oppidum postea magnifice ornavit. In the lifetime of the historian Priscus, Constantine was considered to be the founder of Niš, while Stephan the Byzantine thought that Constantine had created and built up the town. In any case, its cultural and artistic life was developed in the spirit of Christianity.
In order to solve many disputes in the church, Constantine convened the first Ecumenical Council at Nicaea in 325, which was held in the spirit of unity and harmony.
In 330, he transferred the capital of his empire from Rome to Byzantium - Constantinople. Certain historical sources reveal that, pondering about a new capital, he also had his native city Niš in mind.