Just last week, Eastern Orthodox Christians commemorated the entrance of Mary (the Theotokos, “God-birther,” the mother of Jesus) into the Jerusalem Temple. If you’re not familiar with this somewhat surprising story, as many western Christians aren’t, then you may read the tale in the Protevangelium of James, which, while it is certainly an apocryphal text and no part of the canon of Scripture, nonetheless it is recognized to contain many of the same traditions held by Orthodox Christians concerning Mary, which traditions are expressed in hymnography and hagiography. One of these is that Joachim and Anna, Mary’s parents, dedicated her to the Jerusalem Temple as a young girl, where she lived in the Holy of Holies (!) and was fed by an angel. Later, she left the Temple and was entrusted to Joseph. The rest of the story will be familiar.
What is important about this set of stories is its impact particularly among Eastern Christians, particularly early ones (note that the Protevangelium of James dates to roughly the middle of the second century, showing these stories took root very early), and most especially those wealthier among them who were responsible for building churches in the Holy Land. It was believed by early Christians that the child Mary literally lived in the Holy of Holies in the Jerusalem Temple, however unlikely or impossible this was, and however much we may rather prefer to find this allegorically describing her life of faith, purity, and devotion. This led someone, at some point prior to the late fifth century, to construct a Church of Mary Theotokos on the site of the ancient Jewish Temple, the plan of which is, I suggest, preseved by the current Dome of the Rock in Jerusalem.
Several lines of evidence support this:
1.) The foundation of an identical Church of Mary Theotokos precisely atop the ruined Samaritan Temple on Mt Gerizim was built by Emperor Zeno in 484 AD. The choice of a Church of Mary Theotokos there would otherwise be odd, as no traditions relate her life to Gerizim or the Samaritan Temple. Yet, if Zeno were simply treating one set of Temple ruins like another, it would make sense to have the two matching ruins covered with two matching shrines. Thus, the church in Jerusalem will likely have been built earlier than his reign (474-491 AD), though named at the very least if not indeed constructed after the Council of Chalcedon, during which “Theotokos” was argued upon and accepted as the proper Christian title for Mary, indicating Jesus was God and not merely Christ/Messiah. So it was probably built (or at least begun) during the very active construction in the time when the former Empress Eudocia was resident in Jerusalem, roughly 441-460 AD. This founding in the later fifth century would explain why it is not mentioned by Egeria and Jerome.
2.) Justinian’s huge and famous “Nea” church was actually named the New Church of Mary Theotokos, requiring there to be an older church of Mary the Theotokos somewhere in the city, while none is specifically mentioned in the records. The most obvious location would be the Temple Mount, with a Church of Mary Theotokos there to commemorate her living there.
3.) All the known various elements of Mary’s life were commemorated by churches, even a stop for a break between Jerusalem and Ain Karem, the recently rediscovered Kathisma church, also octagonal in plan (as was the original eastern end of the Nativity Basilica in Bethlehem built in the fourth century over the traditional site of the birth cave of Jesus, and the fifth-century structure built over the house of Peter in Capernaum). It is highly unlikely that the otherwise precisely located and unused area of the ruined Jerusalem Temple, based upon the tradition of her childhood there, were not similarly commemorated.
4.) Recent and ongoing sifting of the fill from the Temple Mount has brought to light much evidence of an early Byzantine Christian presence on the platform, in contrast to the former belief that the site was abandoned and used as a dump, which tale was mere propaganda found solely in Islamic sources regarding the building of the Dome of the Rock. (While it is true that every church except the Basilica of the Nativity in Bethlehem was destroyed by the Persians in 614, and thus many churches were still in ruins at the point of the Arab invasion in 638, it does not follow that such ruins were of long standing.) The presence of this memorial Church of Mary Theotokos, undoubtedly one of the pilgrim sites in Jerusalem, would account for these materials.
5.) Further evidence is the choice of Quranic verses for the interior of the Dome of the Rock, denying Jesus being the Son of God, which were chosen not randomly, but in reaction to the former dedication of this church to Mary the Theotokos, which was essentially an important statement about the Son Mary bore being God, and not just a man.
In conclusion, it is, I think, beyond doubt that a Church of Mary Theotokos was constructed in about the middle of the fifth century on the Temple Mount over the ruins of the Jerusalem Temple in order to commemorate the Eastern Christian tradition of Mary having grown up in the Temple itself. It may even have been at that point that the stairway and cave beneath the central rock (the former floor of the Holy of Holies) was cut, in order to provide a “luminous cave” as found in various other of the commemorated Holy Land sites (Annunciation in Nazareth, Nativity in Bethlehem, Eleona on Mt Olivet, Anastasis in Jerusalem, etc), though this may even have been done in Crusader times. The plan of the presently standing Dome of the Rock preserves the plan of this ancient church (and perhaps even some of the structural elements as examination of the beams of the Dome of the Rock indicate they are older than they should be) which would have been destroyed by the Persians, along with most other churches in the Holy Land, only a few decades before the Dome itself was constructed. This makes the Dome of the Rock that much more interesting, I think, in addition to being the most beautiful building in Jerusalem.