Architectural Designs
Ideal Cities, Churches, and Civic Engineering
Let the width of the streets be equal to the average height of the houses.
— Leonardo da Vinci, §746
Overview
Leonardo was never a practicing architect, but his architectural designs — particularly his plans for ideal cities — are among the most forward-thinking proposals in the history of urban planning. After the plague devastated Milan in 1484–1485, he designed a two-level city with separate roadways for pedestrians and vehicles, underground sewage, and canal-based delivery systems for goods.
He also produced centralized church plans, studies for domed buildings, and designs for movable houses. His architectural thinking, like everything else, was driven by observation of how systems actually work — traffic flow, waste removal, light, ventilation.
The Two-Level City
§741–743 — Separating traffic from people
741. The roads m are 6 braccia higher than the roads p s, and each road must be 20 braccia wide and have ½ braccio slope from the sides towards the middle; and in the middle let there be at every braccio an opening, one braccio long and one finger wide, where the rain water may run off into hollows made on the same level as p s. And on each side at the extremity of the width of the said road let there be an arcade, 6 braccia broad, on columns; and understand that he who would go through the whole place by the high level streets can use them for this purpose, and he who would go by the low level can do the same. By the high streets no vehicles and similar objects should circulate, but they are exclusively for the use of gentlemen. The carts and burdens for the use and convenience of the inhabitants have to go by the low ones.
MS. B 15 b
742. …at each arch must be a winding stair on a circular plan because the corners of square ones are always fouled; they must be wide… Let such a city be built near the sea or a large river in order that the dirt of the city may be carried off by the water.
MS. B 16 b
Canals and Streets
§745–746 — A city navigable by boat
745. The front a m will give light to the rooms; a e will be 6 braccia — a b 8 braccia — b e 30 braccia, in order that the rooms under the porticoes may be lighted; c d f is the place where the boats come to the houses to be unloaded. In order to render this arrangement practicable, and in order that the inundation of the rivers may not penetrate into the cellars, it is necessary to choose an appropriate situation, such as a spot near a river which can be diverted into canals in which the level of the water will not vary either by inundations or drought.
MS. B 37 b
746. Let the width of the streets be equal to the average height of the houses.
Leonardo's ideal city is essentially a modern urban planning proposal: separate levels for pedestrians and traffic, underground utilities, waterway logistics. He designed it after watching a plague kill tens of thousands — the city was his public health intervention. The idea of separating vehicle and pedestrian traffic wouldn't be implemented for another 400 years. -D