The Vatican Library preserves a parchment map of impressive dimensions consisting of three joined pieces of vellum. Its contents and graphic characteristics link it closely to the cosmographic discoveries of Fra Mauro (active ca. 1430-ca. 1459/1464), and may well have been a product of his workshop. Oriented with the south at the top of the map and encompassing a geographical area from the Caspian Sea to the Atlantic islands west of the Iberian peninsula, the map features hundreds of place names and 38 cartouches, which, notwithstanding some variations in length and transcription errors, are quite similar to the world map in the Marciana Library.
Although the line is thinner and the images much simpler, many of the illustrations even reproduce the graphic style of the Marciana world map. An important element of this marine chart is the scale of distances, indicated on the narrowest side of the parchment document, with distance expressed in miles. Such a scale is absent from the Marciana world map, but the almost perfect correspondence between the two maps renders the scale equally applicable to both.
The Vatican chart helps us to recognize that the Marciana world map was a point of arrival, a sort of composite of preceding, partial maps, which Fra Mauro mentions in some of his cartouches. Textual variations demonstrate that Fra Mauro had at hand a collection of texts that could be adapted to different types of map, whether nautical or cosmographic.