Notes appear at the bottom of the sketch which outline instructions for how his designs should be implemented. In another similar drawing Leonardo da Vinci would underline the importance of how the addition of a bell tower might disrupt the elegance of his work.

There is plenty of scope for alteration across the stages of an architectural project and perhaps he was concerned this his central idea would be watered down as the building work progressed.

The majority of his drawings for this project included the exterior of the dome area plus also the layout for the floor. In this example Da Vinci would also include some engineering-style outlines of what appears to be some of the internal structures for his buildings. His understanding of the basics of engineering is underlined by some of his insightful inventions, but architectural design is a different discipline that would involve its own considerations.

One aspect of Da Vinci's life that continues to astound is his efficiency and devotion to hard work. For someone to take in so many different disciplines into his career one might expect years of inactivity as he learnt more about each new challenge. To cover so many different things without taking much time to produce more work displays confidence and an ability to learn quickly.

Those who want to see some of Leonardo's work in this series should certainly head to the Bibliotheque de l'institut de France which has a fine selection of many of these drawings, in fact most of them.