An arbalest is a type of crossbow. Leonardo Da Vinci had sketches of a giant crossbow 24 meters across. In Da Vinci pinball the arbalest is a small pinball table underneath the upper playing area. Enter the arbalest board by first lighting the red lights on either side of the arbalest pocket at the right of the lower playing area. Then knock the ball into the pocket and it will go into the lower table.
Once in the arbalest table, use the flippers to knock out the four drop-down targets at the top. A chute will then appear. If you are lucky the chute will appear right under the ball and the ball will go in. Otherwise you need to knock the ball into the chute to get the bonus. The mini-game ends when the ball goes in the chute or goes down the drain between the two flippers.
You can get additional points by lighting all three slots above the upper playing area and activating multipliers for the arbalest drop down targets.