Corner of castle with triple defence system

This building, which was probably made during Leonardo's first Milanese period, depicts a corner of castle with two angular fortifications. Of these, one was contained in the perimeter, the other jutted out of the corner of the fort. The two constructions towered over a moat that was not dug round the building but made by means of a toe wall and an embankment. What is particularly interesting and innovative about this defence system is the location of a row of cannons on the jutting stronghold, in order to be able to shoot at the prospective attackers who climbed the earthwork. This defence system was planned to arrange a sequence of grazing fires aimed at the assault troups in the points where it was difficult to advance - the embankment, the moat, the curtain and the path for walking along the top.