The Cartier Santos Skeleton is a masterclass in horological architecture. Unlike traditional skeleton watches that simply hollow out an existing movement, Cartier’s Caliber 9611 MC was engineered from the ground up so the movement’s bridges form the Roman numeral hour markers. This creates a stunning "floating" effect, making the mechanical heart—gears, mainspring, and escapement—fully visible through the sapphire crystals on both the front and back.