By Mark Duff
BBC News, Milan
Major restoration works were carried out in 2004
Michelangelo's famous statue of David could collapse because of its exposure to mass tourism, Italian experts say.
They say the massive statue of the naked boy-warrior is in danger because of its size, shape and the weakness of the marble from which it was carved.
But they warn that the greatest risk comes from the footfall of many visitors who troop past it each day at Florence's Galleria dell'Accademia.
The experts want to protect the statue by insulating it from the vibrations.
This would cost about 1m euros (£785,000). Otherwise David could topple over, engineers from the University of Perugia say.
The warning follows a detailed study of the statue which showed that the cracks filled during major restoration works four years ago - on the occasion of its 500th anniversary - have already reopened.
That restoration was itself controversial because it involved using distilled water to clean the statue - which critics argued could damage it.
Michelangelo's David has had iconic status almost since its completion at the height of the Renaissance.
At the time it was seen as a powerful symbol of Florence's republican political ideals: David being the youthful warrior who felled the mighty Goliath in the Biblical Old Testament story.
Since then it has enjoyed mixed fortunes: attacked by crowds when it was first displayed, then hacked by a deranged painter in 1991.
The statue has also acquired kitsch status - its copies adorn everything from casinos in Las Vegas to tacky Mediterranean beach bars.