The apse mosaic of S. Apollinare in Classe has often drawn special interest from interpreters due to its extraordinary complexity. Starting from the still unresolved issue of interpreting the relationships between the various image elements, the study examines the liturgical contexts that formed the background for the contemporary viewer as they observed the image. Following systematic analyses of the iconographic traditions on one hand and the liturgical matters on the other, structural correspondences between the image form and liturgical meanings are clarified, which prove to be relevant for understanding the overall image.