After Filarete's project for Sforzinda, an ideal city in honor of Francesco Sforza, Leonardo, as well, was fascinated by the idea of planning a city as a formally complete organism. The waterways are as important as the streets, but
"if you want this to have effect […] you must choose an appropriate site, for example, placing it next to a river that will provide you for canals …"
Milan's problem was the lack of a large river with a constant flow like the Ticino. Leonardo indicated this in his projects, possibly thinking of a new role for Vigevano, a city favored by Ludovico Il Moro.