This carefully drawn and coloured map shows the stretch of the river Arno immediately to the west of Florence - the key area in the Florentine Republic’s efforts to make the Arno a navigable waterway connecting Florence to the sea.

In Leonardo’s bird’s-eye vision, the waters of the Arno course through the living body of the earth just as veins run throughout the human body. Tiny dots visible within two parting streams of the Arno, towards the upper centre of the drawing, represent sediment deposits laid down by the river at the mouth of the tributary.