The Great Bird was a mechanical flying apparatus invented by Leonardo da Vinci.
In 2374, USS Voyager Captain Kathryn Janeway and the Leonardo da Vinci hologram from one of her holodeck programs attempted to launch a prototype of the glider from a bridge in Florence. They immediately fell into the Arno and had to retreat in embarrassment to da Vinci's workshop.
Later, when the hologram was stolen from Voyager by spacefaring pirates and outfitted with The Doctor's mobile emitter, he spent several days on a trading center planet, where he rebuilt his "Great Bird" using duranium. He and Janeway used it to escape pursuers after they had recovered Voyager's stolen goods. The "Great Bird", with Janeway and da Vinci aboard, was beamed from mid-air to Voyager's cargo bay. (VOY: "Concerning Flight")