A section of the "Madaba Map," a 6th century CE mosaic rendering of the Middle East.
The map, on the floor of the Basilica of St. George, would have been quite an attraction to Byzantine era pilgrims.
The section shown here is, I believe, Jerusalem.
According to Wikipedia:
"With two million pieces of colored stone, the map depicts hills and valleys, villages and towns in Palestine and the Nile Delta.
The mosaic contains the earliest extant representation of Byzantine Jerusalem, labeled the 'Holy City' (Madaba, Map)."