The paper summarises the eleven-year activity of the International Committee for Safeguard and Stabilisation of the Leaning Tower of Pisa. After a description of the Tower, of its history and of the related subsoil conditions, the paper focuses on the intervention that been implemented with the aim to stop the progressive increase of the inclination, which was jeopardising the survival of the Tower. The method chosen to stabilise the Tower consisted in highly controlled ground extraction, named underexcavation, which by inducing the settlement of the North edge of the plinth, allowed to reduce the inclination of the Tower by 1800 arc-seconds, one tenth of the maximum tilt, recorded in 1993. This intervention is now leaving the Tower in the same situation of the beginning of XIX Century.
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