The iconostasis (sl: ikonostas), or icon screen, is one of the most important architectural features of Eastern Christian churches. It is an unbroken screen, composed of icons, that separates the sanctuary, where the sacrament of Eucharist is celebrated, from the central part, or nave, where the congregation stands.   While the ikonostas symbolically separates the heavenly world (the altar area) from the human world (the main body of the church) it also unites these two worlds into one.
The ikonostas of St. Mary's church is a full Slavic ikonostas consisting of three doors and four tiers of icons.   The icon screen has double doors in the center and single doors on either side.   The double doors are called the Royal or Holy Doors because the Holy Eucharist and only the bishop or priests can pass through them.   They are decorated with icons of the four evangelists Luke, Matthew, Mark, and John.   These doors are most often also decorated with an icon of the Annunciation.   The Royal Doors also represent the gates of Heaven.
The single doors on either side of the Royal Doors are known as the Deacon door and the Service door.   The Deacon door, to the right of the Royal Doors, is decorated with an icon St. Stephen the Protomartyr, while the Service door, to the left of the Royal Doors, is decorated with an icon of St. Michael the Archangel.
In addition to the icons on the doors, the first tier also contains four Main Icons, (Namistnyi Ikony) in Slavonic.   To the immediate right of the Royal Doors is an icon of Jesus Christ, Pantocrator, while to the far right is an icon of the patron saint of the parish, in this case the icon of the Protection of the Mother of God (Pokrova).   To the immediate left of the Royal Doors is the icon of the Virgin and Child.   At the far left is an icon of St. Nicholas the patron saint of the the Byzantine church. If the parish has St. Nicholas as their patron saint then an icon of St. John the Baptist usually occupies the far left position of the first tier.
The second tier of the ikonostas contains icons of the twelve major feast days of the Byzantine liturgical year, with an icon of the Mystical Supper in the middle. The icon of the Mystical Supper is given a place of prominence, directly above the Royal Doors, since this event is reenacted during every Liturgy and should be a focal point of the ikonostas.   The major feast days depicted to the left of the Mystical Supper icon are (l. to r.) Dormition of the Mother of God; Descent of the Holy Spirit (Pentecost); Presentation of Christ in the Temple; Annunciation; Presentation of Mary in the Temple; and The Nativity of Mary.   To the right of the Mystical Supper icon the major feasts are as follows (l. to r.) The Nativity of Jesus Christ; Baptism of Christ (Epiphany); Transfiguration; Entry into Jerusalem (Palm Sunday); Ressurection; and Ascension.
The third tier of icons is that of the Apostles of Christ namely, (l. to r.) St. Thaddeus (Jude); St. James, the son of Zebedee; St. Thomas; St. Simon; St. Andrew; St. Peter; St. Paul; St.James, the brother of the Lord; St. Phillip; St. Bartholomew; St. Matthew; and St. John.
The fourth tier consists of icons of the Old Testament prophets and patriarchs shown in groups of two namely (l. to r.) (Zecharius & Samuel); (Daniel & Habakkuk); (Moses & David); (Solomon & Ezekiel); (Haggai & Elias); and (Elisha & Zechariah).
Betwen the third and fourth tiers, and above the icon of the Mystical Supper, is a large icon of Jesus Christ, the High Priest, seated on a throne as Lord of the Universe.   Above the large icon of Christ is a cross with an icon of the Crucifixion.   To the left of the cross is an icon of the Mother of God, while to the right is an icon of St. John the Evangelist.   On the horizontal cross arm are affixed icons of St. Constantine (left) and St. Helena (right).
This full, Slavic, ikonostas, in addition to the icons, is constructed with intricately carved wooden grapevines with long intertwined branches, wide leaves and clusters of grapes that symbolize our union with Christ Who said "I am the vine and you are the branches". (Jn. 15:5)