Leonardo was known to dislike the state of urban living, describing cities as old fashioned, where people lived crammed together "like a herd of goats." After Filarete's project Sforzinda, Leonardo was also fascinated by the idea of creating a complex, perfect city. The design combines Da Vinci's wide range of talents, and shows his mastery of architecture, engineering, and art. The phrase ideal city refers to perfection of the 'machinery' of the city. His design utilized his invention of locks to make waterways efficient while keep the city's inhabitants safe from violent floods of water. There was also a strong emphasis on hygiene in his design, which included mechanisms for keeping the streets clean as well as preventing water and waste to stagnate. Da Vinci mentions that he believes the city should be cleaned at least once a year. His city's transportation network included different level streets for different purposes of transportation. Overall, his design focused on the possibilities of geometrically perfect solutions to the predicaments of urban life. 

Sources:

“The ideal city – Ms B Fol 16r and 37.” Universal Leonardo, University of Arts, London, www.universalleonardo.org/work.php?id=519.

“The Ideal City.” Museoscienza, Museo Nazionale della Scienza e della Technologia "Leonardo DaVinci", www.museoscienza.org/english/leonardo/invenzioni/citta.asp.

Image Source: "The Ideal City", www.leonardo3.net