7. The Leaning Tower of Pisa
The identity of the famous tower of Pisa’s original designer remains uncertain, by the dawn of the twenty-first century it was argued that the tower was designed by an Italian architect named Diotisalvi, rather than the long attributed Bosanno Pisano. Whoever designed it and began construction in 1173 didn’t live to see it completed, it was 199 years before the structure was finished. During the first phase of construction, the tower began to sink, due to its being provided with an inadequate foundation on unstable soil. Construction was then halted for nearly a century, with three floors complete. When construction began again in 1272, floors were deliberately designed to have one side taller than the other, to compensate for the lean of the tower.
The tower continued to increase its lean, though gradually, throughout its history until 2008. Stabilization efforts and anchoring it with cables were completed in the 1980s and 1990s, and buildings which would be in the way should the tower fall over were evacuated. The tower was pulled back towards the vertical in the 1990s, though it was allowed to keep it’s distinctive lean, once it reached a position which was deemed safe by structural engineers. The lean was corrected by removing supporting soil under the raised end of the tower. When the work was completed it was announced that the tower would remain stable for three centuries. Seven years later that estimate was reduced to 200 years.