An open question: do the five bays of St. Mark’s facade represent the five domes capping the church?
Is this mosaic a section?
Or is this facade itself a cut-away view of a larger church? A doubled San Marco sitting in the square?
The facade, oddly, is disconnected from the interior spaces (in plan, the facade arcade wraps a more-traditional cross). While the bay structure corresponds to the over grid of the plan, the placement of the half-domes represented on the facade is off. It’s fascinating to imagine that this separation inspired the architects to represent the domes of the church on a flattened plane, turning the main facade into a representation of the building itself: