Michelangelo's David

Although touted for being an anatomical marvel, Michelangelo’s David has a ‘hole’ in the back.
Computer measurements of David’s body taken by Italian scientists at Florence University showed a hollow instead a muscle on the right side of the back, between the spine and the shoulder blade.
However, Michelangelo was aware of the mistake, and wrote in a letter that a defect in the marble block made it impossible to reproduce the muscle.