Leonardo da Vinci designed a revolving bridge to rotate around a central support for military crossings.
The bridge appears among his engineering proposals for the Duke of Milan, Ludovico Sforza. Its rotating structure was intended to let an army cross a waterway and then be swung aside, allowing boats to pass and making the crossing easier to defend. Leonardo’s drawing includes a counterweight and a mechanism designed to help one operator move the bridge.
Unlike a fixed bridge, this concept combined transport with controlled access. A movable bridge could be useful in wartime because it reduced the need to leave a permanent crossing in place. Leonardo also emphasized portability and rapid deployment, themes common in his military engineering work.
The design is often mistaken for a drawbridge. A drawbridge normally lifts or pivots upward, while Leonardo’s proposal turned horizontally around a pivot. It was a design study rather than a documented bridge built and used by Leonardo’s army.