On map RL 12278 (Windsor Castle) Leonardo very clearly evidences the city of Chiusi, a centre of primary importance since Etruscan times, as shown by its numerous treasures now in the local National Museum and the Florence Archaeological Museum. The decline of the city, beginning in the Middle Ages, was caused by the swamps that progressively invaded the Val di Chiana. Chiusi is recalled by Leonardo, in the early 16th century, in Ms. L (f. 94v) in which he describes the itinerary from Buonconvento to Chiusi and from there to Foligno. The rediscovery of the Etruscan civilization also exerted its influence on Antonio da Sangallo the Younger and Leonardo, as exemplified for the latter by the study on the mythological tomb of King Porsenna found in the Codex Atlanticus.
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