Da Vinci wrote in his notebooks some ideas for creating an ideal city. Due to lack of space in Europe, the city was never created.
Since you are in the process of building a city, here is a guide to how to make your city as great as Da Vinci.
Step 1: Underground and Water System
The first step to building Da Vinci's city is to build a sewer. It would help if the city was on a river so that water can freely run underneath the city taking with it the waste from the city.
Also underground, build hydraulic machines to distribute running water into all of the buildings. Use a mechanical lifting system to give every building running water. It can also be used to power machines inside of factories.
Build two levels of canals, connected via pipes and archways. The lower levels will be large tunnels with water running through. All waste will go through these underground canals.
Step 2: Canals and Roads
Canals and roads will be necessary for the city for both transportation and hygiene.
Dig both "upper canals" and "lower canals" to separate the tradesmen from the gentlemen and to reduce traffic. These canals will be just as important as roads for commercial purposes.
Also build roads through the city. All the roads must be 12 meters wide. This is enough that people can freely travel without spreading disease through contact. Streets must slope toward the middle where drains will take street waste and rain water into the sewage system.
Build a paddlewheel (above) to filter the canal water to keep the city clean and garbage free. It will also be used to clean the streets.
Step 3: Locks
Because the canals will have two levels, a lock system will be used to manage the navigation on different levels.
Build a set of locks (pictured above) that allow boats to be lowered to the underground level. Once there, the canals will lead boats under the buildings so that they may travel freely under the city.
Step 4: Animals
Animals are an integral part of any city. They provide food, farm labor, and even transportation. To avoid plague, the animals must have their own space in a city.
Build stables and farmhouses just outside of the city so that animals are present but not inside of the city. Use canals for easy access to the stables.
If animals need to be in the city for any reason, have them use the bottom level to keep the top area for the "gentlemen" clean.
Step 5: Beautiful Buildings
The best cities have the best architecture. Arches and pillars must be used to make the city as beautiful as possible.
Build piazzas that connect the upper and lower sections of the city. This way the gentlemen can look down upon the lower part of the city.
Every single building must have good ventilation to ensure that diseases are not trapped in homes. To do this include windows or halls that can have cross breeze to carry out stale air.