San Vitale's presbytery is Byzantine wall mosaic at full strength — roughly one-centimetre glass tesserae bedded at deliberate angles so light rakes across the surface instead of lying flat on it. The vault alternates two grounds: gold leaf fused between clear glass, and a deep green field carrying the paradise meadow.
This system takes that construction literally. Gold is built from discrete faceted cells, never a gradient. Every edge is seamed with mortar dark. Nothing blurs, nothing glows — the shimmer comes from variation between cells.