LEANING TOWER OF PISA

Italian Torre Pendente Di Pisa, medieval structure in Pisa, Italy, that is famous for the settling of its foundation, causing it to lean 17 feet (5.2 m) from the perpendicular. The bell tower, begun in 1174 as the third and final structure of the city's cathedral complex, was designed to stand 185 feet (56 m) high and was constructed of white marble. Three of its eight stories were completed when the uneven settling of the building's foundation in the soft ground became noticeable. Bonnano Pisano, the engineer in charge, sought to compensate for the lean by making the new stories slightly taller on the short side, but the extra masonry caused the structure to sink still further. Work was suspended several times as engineers sought solutions, but the tower was ultimately topped out in the 14th century, still leaning. In modern times the foundations have been strengthened by the injection of cement grouting, but in the late 20th century the structure was still in danger of collapse, and various schemes were being considered to save it.