White marble campanile in Pisa, Italy, famous for the uneven settling of its foundation, which caused it to lean 5.
5 degrees (about 15 ft [4.5 m]) from the perpendicular. Begun in 1173 as the third and final structure of the city's cathedral complex, it was designed to stand 185 ft (56 m) high. Work was suspended several times as engineers sought solutions; the tower, still leaning, was completed in the 14th century. Subsiding at the rate of 0.03 in (1.2 mm) a year, the structure was in danger of collapse, and in 1990 it was closed as engineers undertook a strengthening project that decreased the lean by 17 in (44 cm) to about 13.5 ft (4.1 m). The work was completed in May 2001.