The viola organista is one of many Leonardo da Vinci creations that never left the design phase, but 500 years after it was dreamed up someone has finally built the quirky instrument. Described as a cross between a piano and a cello, the instrument took concert pianist Slawomir Zubrzycki three years and approximately 5,000 hours of work to complete. Records of it began with da Vinci's Codex Atlanticus journal, which features notes and sketches dating from 1478 to 1519, covering everything from mathematics to flying machine concepts.

"I'd hope he'd be pleased."

The keyboard features four spinning wheels, each pulling a bow made of horse hair. Pumping a pedal keeps them rotating, while pressing the keys pushes down on the wheels, producing the instrument's unique sound. "I have no idea what Leonardo da Vinci might think of the instrument I've made, but I'd hope he'd be pleased," Zubrzycki says. da Vinci was never able to hear what his creation sounded like, but you can, as Zubrzycki didn't just build the viola organist, he also played it — you can check out its beautiful debut performance at the Academy of Music in Krakow below.