The depictions of Gabriel and Maria are in fact a single iconographic image - the Annunciation, one of the important events in the liturgical calendar portraying the moment when the archangel appears to Maria and informs Her She is to give birth to Jesus. The early Russian churches adopted from Byzantium the practice of displaying the Annunciation as it is here--flanking the opening to the Sanctuary. Since Byzantine artistic norms after the iconoclast controversy forbade three-dimensional portayals of holy figures, the Byzantine artists devised a way to combine the two dimensionality of individual paintings with the three-dimensional space created by the architecture. Thus the Annunciation "takes place" in three dimensional space and in a sense invites the believer's gaze into the main apse, where the key elements of the Christian theology would be represented in additional images and in the liturgy itself.