Fortified gate, moat and treachery-proof tower
Plans of a moat, gate and rivellino with a tower split into eight stairs so no traitor can seize it
The sheet lays out a fortress gate defended by a moat and outwork (rivellino), a tower shown in elevation and plan, and a circular tower drawn in section. Its long note explains a scheme to make a sea-set tower proof against treachery: by dividing it into eight spiral staircases and eight separate quarters, a single bribed garrison man can never join others on the walls, while the castellan above commands murder-holes, portcullises and smoke to purge the stairs. The drawings label the main road, the road along the ditches, and the gate.
On this page
Plan of a moat, gate and rivellino
A ground plan sets a gate behind a moat and a projecting outwork. It is labelled with the main road, the road running along the ditches, and the gate itself.
Tower in elevation and plan; locking the gate
A tower is drawn both in elevation and in plan. The note marks the wall and points to a way of locking the gate.
Tower section split into eight spiral stairs against treachery
A round tower is sectioned to show a defence against betrayal from within. Leonardo divides it into eight spiral staircases and eight separate soldiers' quarters, so a traitor cannot rally others on the walls; the castellan above can drive attackers off with murder-holes and portcullises and choke the stairs with smoke.