What type of weapon was Leonardo da Vinci’s Architonnerre?

Leonardo da Vinci’s Architonnerre was a steam cannon concept.

The design described a heated chamber in which water would turn into steam. The expanding vapor was intended to force a projectile from a barrel, replacing the explosive charge used in a conventional gun. Leonardo’s notes reflect his interest in adapting ancient accounts of steam-powered artillery into a more detailed machine.

The Architonnerre is generally associated with Leonardo’s military and mechanical studies, but it was not a proven battlefield weapon. Surviving drawings and descriptions show an ambitious concept rather than a documented, operational cannon.

It is easy to confuse the Architonnerre with Leonardo’s many gunpowder weapons, including multi-barreled guns and large crossbows. Its defining feature is proposed steam pressure, not a rotating barrel or a giant bow.