NGM Blog Central - Full Tilt - National Geographic Magazine

Of all Pisa’s leaning towers—yes, there are several—the famous one is the least likely to topple. That’s because an 11-year restoration effort, involving three years of painstaking soil removal, has successfully steadied the precariously poised campanile. Pisa’s soil is mostly compressible clay and sand, which gives way over time and causes big buildings to shift.

The iconic edifice started listing northward during its first phase of construction, in the 1100s, then changed course, pitching southward over the next eight centuries. An 1817 measurement put its incline at 5 degrees; by 1990, the cant had increased to 5.5. Fearing the 197-foot-tall, tourist-luring monument might collapse, Italy’s premier formed an international team to preserve it. John Burland, a top project engineer, says the tower’s tilt is back to 5 degrees, and “over the last two years, almost no movement has been detected.” The city’s other bell towers, though linked to larger structures, haven’t been bolstered. One hopes the Leaning Tower of Pisa won’t someday be the Only Tower of Pisa. —Catherine L. Barker

Photos: (Left) La Torre di Pisa: year completed: circa 1370; tilt: 5 degrees. (Middle) San Nicola: year completed: circa 1250; tilt: 2.5 degrees. (Right) San Michele degli Scalzi; year completed: circa 1100; tilt: 5 degrees.

Photographs by Gianluca Colla

Art: Mariel Furlong, NG staff

Posted by National Geographic Staff | Comments (0)
Filed Under: Technology, Wide Angle

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