Helena, mother of Constantine I in the context of "Saint Helena"

Constantine I (27 February 272 – 22 May 337), also known as Constantine the Great, or known mononymously as Constantine, was Roman emperor from AD 306 to 337 and the first Roman emperor to convert to Christianity. He played a pivotal role in elevating the status of Christianity in Rome, the Edict of Milan decriminalising Christian practice and ceasing Christian persecution. This was a turning point in the Christianisation of the Roman Empire. He founded the city of Constantinople (now Istanbul) and made it the capital of the Empire, which it remained for over a millennium.

Born in Naissus, a city located in the province of Moesia Superior (now Niš, Serbia), Constantine was the son of Flavius Constantius, a Roman army officer from Moesia Superior, who would become one of the four emperors of the Tetrarchy. His mother, Helena, was a woman of low birth, probably from Bithynia. Later canonised as a saint, she is credited for the conversion of her son in some traditions, though others believe that Constantine converted her. He served with distinction under emperors Diocletian and Galerius. He began his career by campaigning in the eastern provinces against the Persians, before being recalled to the west in AD 305 to fight with his father in the province of Britannia. After his father's death in 306, Constantine was proclaimed as augustus (emperor) by his army at Eboracum (York, England). He eventually emerged victorious in Civil wars of the Tetrarchy against the emperors Maxentius and Licinius to become the sole ruler of the Roman Empire by 324.

In Christian tradition, the True Cross is the original wooden cross on which Jesus of Nazareth was crucified.

It is related by numerous historical accounts and legends that Helen, the mother of Roman emperor Constantine the Great, recovered the True Cross at the Holy Sepulchre in Jerusalem, when she travelled to the Holy Land in the years 326–328. The late fourth-century historians Gelasius of Caesarea and Tyrannius Rufinus wrote that while Helen was there, she discovered the hiding place of three crosses that were believed to have been used at the crucifixion of Jesus and the two thieves, Dismas and Gestas, who were executed with him. To one cross was affixed the titulus bearing Jesus' name, but according to Rufinus, Helen was unsure of its legitimacy until a miracle revealed that it was the True Cross. This event is celebrated on the liturgical calendar as the Feast of the Exaltation of the Cross (Roodmas) by the Oriental Orthodox, Eastern Orthodox, Persian, Roman Catholic, Lutheran, and Anglican churches.

During the reign of the Roman emperor Constantine the Great (306–337 AD), Christianity began to transition to the dominant religion of the Roman Empire. Historians remain uncertain about Constantine's reasons for favoring Christianity, and theologians and historians have often argued about which form of early Christianity he subscribed to. There is no consensus among scholars as to whether he adopted his mother Helena's Christianity in his youth, or, as claimed by Eusebius of Caesarea, encouraged her to convert to the faith he had adopted.

Constantine ruled the Roman Empire as sole emperor for much of his reign. Some scholars allege that his main objective was to gain unanimous approval and submission to his authority from all classes, and therefore he chose Christianity to conduct his political propaganda, believing that it was the most appropriate religion that could fit with the imperial cult. Regardless, under the Constantinian dynasty Christianity expanded throughout the empire, launching the era of the state church of the Roman Empire. Whether Constantine sincerely converted to Christianity or remained loyal to paganism is a matter of debate among historians. His formal conversion in 312 is almost universally acknowledged among historians, despite that it was claimed he was baptized only on his deathbed by the Arian bishop Eusebius of Nicomedia in 337; the real reasons behind it remain unknown and are debated also.

Calvary (Latin: Calvariae or Calvariae locus) or Golgotha (Biblical Greek: Γολγοθᾶ, romanized: Golgothâ [Κρανίου Τόπος or Κρανίο]) was a site immediately outside Roman Jerusalem's walls where, according to Christianity's four canonical gospels, Jesus was crucified.

Since at least the early medieval period, it has been a destination for pilgrimage. The exact location of Calvary has been traditionally associated with a place now enclosed within one of the southern chapels of the multidenominational Church of the Holy Sepulchre, a site said to have been recognized by the Roman empress Helena, mother of Constantine the Great, during her visit to the Holy Land in 325.

The Church of the Nativity, or Basilica of the Nativity, is a basilica located in Bethlehem, West Bank, Palestine. The grotto holds a prominent religious significance to Christians of various denominations as the birthplace of Jesus. The grotto is the oldest site continuously used as a place of worship in Christianity, and the basilica is the oldest major church in the Holy Land.

The church was originally commissioned by Constantine the Great a short time after his mother Helena's visit to Jerusalem and Bethlehem in 325–326, on the site that was traditionally considered to be the birthplace of Jesus. That original basilica was likely built between 330 and 333, being already mentioned in 333, and was dedicated on 31 May 339. It was probably destroyed by fire during the Samaritan revolts of the sixth century, possibly in 529, and a new basilica was built a number of years later by Byzantine Emperor Justinian (r. 527–565), who added a porch or narthex, and replaced the octagonal sanctuary with a cruciform transept complete with three apses, but largely preserved the original character of the building, with an atrium and a basilica consisting of a nave with four side aisles.