When construction resumed in 1272, the additional developments did not exactly help the tower’s posture. The stacking of additional stories atop the existing three jostled the building’s center of gravity, causing a reversal in the direction of its tilt. As the tower accrued its fourth, fifth, sixth, and seventh stories, the once northward-leaning structure began to tip further and further south.
As time passed, the ground only further weakened beneath the tower’s heft. An early 0.2-degree tilt increased gradually over the subsequent centuries, maxing out at 5.5 degrees—or with the top 15 feet south of the bottom—by 1990. Over the next decade, a team of engineers leveled the soil beneath the tower and introduced anchoring mechanisms in an effort to rectify the landmark’s nearly catastrophic lean. The project allotted the tower a more secure stance, but it did not prevent continued tipping. By 2008, however, a second go at balancing the foundational soil halted the tower’s continued slouching for the first time ever.
A number of other Pisani structures suffer foundational instability thanks to the river city’s soft grounds. Among these are San Nicola, a 12th century church located about half a mile south of the Leaning Tower of Pisa, and San Michele degli Scalzi, an 11th century church about two miles east of the pair. While San Nicola, whose base is rooted beneath the earth, leans only mildly, San Michele degli Scalzi boasts a substantial 5-degree tilt.
