Topological Diagrams

Before maps entered schools, educators used topological diagrams to explain events described in books or to lay out a basic knowledge of how the world is organized. The most celebrated topological diagrams to survive from the Roman past are the mappaemundi, of which at least two are preserved as they would have been used in late antiquity and without medieval additions:

Babylonian examples. Solinus. The Commentaries on Lucan.

A topological diagram could be described as a reduced cartographic chart in which nothing else but the spatial relationships between a few selected points is shown. Diagrams of urban transport systems are the most common topological charts in use today: they show only the stops, which are arranged along smooth lines to emphasize the sequences and connections and eliminate any other information which might confuse the user. System diagrams name all the points, but do not show true distances or apply a consistent north orientation.