Eusebius of Caesarea
Life of Constantine 3,43 (335 AD)
The Constantinian-era historian Eusebius, author of a biography of that Byzantine emperor, devoted a large amount of space in his chronicles to describing the Holy Places and the churches built there by Constantine.
In terms of the Church of the Nativity, the historian described the architectural evolution of the holy place from a bare cave to the construction of the Constantinian church.
Construction of the Constantinian church
She [Constantine’s mother] immediately consecrated two shrines to the God whom she adored, one at the cave in which the Lord was born, the other on the mountain from which he ascended to heaven. For he who was “God with us” had allowed himself to suffer even birth for our sake, and the place of his birth is called Bethlehem by the Hebrews. Accordingly, the most pious Empress honored the Godbearer’s pregnancy with wonderful monuments, embellishing the sacred cave with all possible splendor. And soon thereafter the emperor himself honored it with imperial offerings, adding to his mother’s works of art with costly presents of silver and gold and embroidered curtains.