1. Michelangelo's masterpiece statue "David" is in great danger of collapsing due to its weak ankles and the structure's 5.5-ton weight. Scientists have confirmed that cracks in the heels of the giant 5.17-metre-tall iconic statue make it susceptible to crumbling under its own weight. The cracks have become the statue's Achilles heel. Tests carried out by Italy's National Research Council and Florence University confirmed the existence of a whole series of "micro-fractures" that have weakened David's ankles. A number of factors have led to this weakening. These include the poor quality of marble and the fact that the statue has been leaning at an angle for centuries, and vibrations from traffic and museum visitors.