April 2, 1968 A.D. the Blessed Virgin Mary began appearing on top of the Coptic Orthodox Church in the Zeitoun District of Cairo, Egypt. An estimated one million people were able to witness the numerous Marian apparitions that occurred during a two year stretch ending in 1971 A.D.
Both Christians and Muslims witnessed Our Lady of the Light appear on top of the domed church. Even then President Nasser of Egypt witnessed it himself and ordered a complete investigation, intimidating and pilfering the church. They came up with no evidence of any hoax. In the end even he, a Muslim, admitted to this reality.
From my limited understanding, this is the only instance I can recall where the Blessed Virgin Mary appeared in front of largely non-Catholics. In my humble opinion is that the Coptic Orthodox Church of Alexandria was founded by Saint Mark the Evangelist, the one and only of the same gospel, and that many, many saints were buried beneath that church in Zeitoun, Egypt.
Hence the special importance of why the Blessed Virgin Mary chose that particular church, the Virgin Mary Church in Zeitoun. Having an unbroken apostolic tradition with the blood of many martyrs sanctifying the beautiful church where these apparitions occurred.
(Biretta Tip: Canterbury Tales)
To learn more about the apparitions of the Virgin Mary in Zeitoun, Egypt, click here.