 none of his building projects was actually carried out as he devised them, but in his architectural drawings, however, he demonstrates mastery in the use of massive forms, clarity of expression, and especially a deep understanding of ancient Roman sources;

Scientific and Theoretical Projects
 as a scientist Leonardo towered above all his contemporaries; his scientific theories, like his artistic innovations, were based on careful observation and precise documentation;
 unfortunately, he never completed his planned treatises on a variety of scientific subjects; his theories are contained in numerous notebooks, most of which were written in mirror script; because they were not easily decipherable, Leonardo's findings were not disseminated in his own lifetime; had they been published, they would have revolutionized the science of the 16th century;
 Leonardo actually anticipated many discoveries of modern times: in anatomy he studied the circulation of the blood and the action of the eye; he made discoveries in meteorology and geology, learned the effect of the moon on the tides, foreshadowed modern conceptions of continent formation, and surmised the nature of fossil shells; he was among the originators of the science of hydraulics and probably devised the hydrometer; his scheme for the canalization of rivers still has practical value; he invented a large number of ingenious machines, many potentially useful, among them an underwater diving suit; his flying devices, although not practicable, embodied sound principles of aerodynamics.

Leonardo's machines
Leonardo's output is the expression of the men and women of the time, of what they felt and did, of the machines they built so that in turn they could build churches, palaces, fortresses; machines for waging war, for work, for the manufacture and trade of all those goods whose availability was of such great importance to the rulers and their courts. Leonardo embarked upon his own path of research and drawing up of ideas and plans embracing a multitude of sectors, ranging from hydraulics to mechanics, to flight, to anatomy and to optics.. Flying Machines
ANEMOMETER
It is made up of a wooden graduated framework with a vane, which is turned by the wind so as to show its direction. This instrument was designed to study weather conditions, with a view to improving safety in human flight.
ANEMOSCOPE
Another flight instrument designed for indicating the direction of the wind. This is one of those devices, which Leonardo deemed necessary for human flight, in that they gave an insight into the characteristics of the air or the wind.
AERIAL SCREW
This is one of Leonardo's best-known designs. Some experts have identified it as the ancestor of the helicopter. Aerial screw would be made of reed, linen cloth and wire, with a diameter of 5 meters, operated presumably by four men who might have stood on the central platform and exerted pressure on the bars in front of them with their hands, so as to make the shaft turn. A machine thus designed would probably never have risen off the ground or been set moving; the idea remains, however, that if an adequate driving force were applied, the machine might have spun in the air and risen off the ground. The aerial screw differs from the other machines in that it was planned for the study of the propeller's tactile efficiency and not as a real flying machine. In the note accompanying the drawing, Leonardo, in fact, suggests that, by way of example, what he claims can be experimented by taking a thin, wide rod and rotating it fast in the air. This will prove that the arm of the person rotating the rod will be pulled upward towards the rod itself. In the same note, Leonardo suggests making a paper model of a screw and launching it by means of a coil spring wrapped around the base of the screw. The specific mentioning of the screw strengthens the assumption that this model was actually a representation of the windmill game, a toy that was already popular in Leonardo's age. Due to its small size, the toy could be operated by a spring or, better still, by a small rope, the fast unwinding of which turned the screw and made it move upward. This might be the source of the intuition that the same mechanism, larger in size and operated by an adequate driving force, could have risen off the ground. FLYING SHIP
Small flying ship equipped with flapping wings and helm.