To modern eyes, mappae mundi can look superficially primitive and inaccurate. However, mappae mundi were never meant to be used as navigational charts and they make no pretence of showing the relative areas of land and water. Rather, mappae mundi were schematic and were meant to illustrate different principles. The simplest mappae mundi were diagrams meant to preserve and illustrate classical learning easily. […]
The larger mappae mundi have the space and detail to illustrate further concepts, such as the cardinal directions, distant lands, Bible stories, history, mythology, flora, fauna and exotic races. In their fullest form, such as the Ebstorf and Hereford maps, they become minor encyclopedias of medieval knowledge.
Source: Mappa mundi – Wikipedia