St Petersburg Institute of History, Russian Academy of Sciences
This map was prepared by Giovanantonio Maiollo, a hereditary cartographer of the Genoese school of mapmaking.
The sheet of parchment has preserved an indistinct depiction of the Virgin and Child and a three-line inscription which tells us who made the given map and when. The map is oriented to the North. It shows eight compass roses with 32 points. The two principal roses have letters signifying the sides of the world. The six other roses have a lily, which was the family symbol of the Maiollos., who were very likely of Catalan ancestry. The smallest rose is located on the site of Rome. The two leading ports of the Mediterranean-Pontic basin - Genoa and Venice - are distinguished by their flags and recognizable views of the cities. At the top and bottom of the map there are scale lines. At the root of scale lines, wherever they were made, is the single measure of distance that was presumably Catalan.
All such maps of the Mediterranean and Black Seas have identical configurations. Almost nothing changed till the end of the 16th century in the way they presented the small islands and capes. Surely in all of these compass maps the drawings of these seas repeat a certain prototype which was based primarily on information gathered second-hand. Such a prototype may have been a Catalan map dating from the second half of the 13th century which even the most qualified later cartographers did not alter and did not correct.