The single most important piece of Byzantine Christian mosaic art in the East is the Madaba Map, made between 542 and 570 as the floor of the church of Saint George at Madaba, Jordan. It was rediscovered in 1894. The Madaba Map is the oldest surviving cartographic depiction of the Holy Land. It depicts an area from Lebanon in the north to the Nile Delta in the south, and from the Mediterranean Sea in the west to the Eastern Desert. The largest and most detailed element of the topographic depiction is Jerusalem, at the center of the map. The map is enriched with many naturalistic features, like animals, fishing boats, bridges and palm trees

What is the most important mosaic piece built by Byzantine Christians?