The Cartier Ballon Bleu is a classic watch series by Cartier, renowned for its distinctive round case, cabochon crown set with a sapphire, and Roman numeral hour markers. Inspired by the historic Montgolfier blue balloon, an early human-flight invention, the design features a curved case, blued steel hands, and a seamless blend of elegance and technological flair. Crafted in stainless steel, rose gold, or diamond-set variations, it is a unisex timepiece and one of the brand’s most iconic luxury watches.