From the campo, San Pantalon looks like a church forgotten halfway: a wall of raw bricks, without a façade, that promises nothing. But whoever passes through the portal finds themselves beneath the largest canvas painting in the world: 443 square metres of Baroque illusion, the Martyrdom and Glory of St Pantaleon that Gian Antonio Fumiani pursued for twenty-four years and — legend has it — ended up paying for with his life.