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Soon after building started in 1173, the foundation of the Pisa tower settled unevenly. Construction was stopped, and was continued only a 100 year later. It then became visibly clear that the Tower of Pisa is leaning, tilting to the south.
Since regular measuring of the tower began in 1911, the top of the tower has moved 1,2 millimetres (0,05 inch) per year. Today the top of the Tower of Pisa is some 5,3m (17,4 ft) off-center.
