The Tower of Pisa has been called “the world's most famous construction mistake” and “the world's longest-standing impending structural collapse.” Yet it remains upright in spite of its age and precarious lean, not to mention the numerous invasive restoration projects it has endured. Ironically, it took the 1989 collapse of the mundanely perpendicular Civic Tower in Pavia, for Italians to get serious about stabilizing their country's most famous architectural structure. From early 1990 until December 2001 it remained closed to the public while engineers implemented a complex $30 million rescue plan. The Tower of Pisa still looks as if it might collapse at any moment, but in reality, it is more stable now than at any time in the past few centuries.
In the recent book “Tilt: A Skewed History of the Tower of Pisa” (Simon & Schuster), author Nicholas Shrady recounts the history of the Tower of Pisa in all of its off-kilter glory. Fittingly, “Tilt” has a difficult-to-describe slanted binding that makes it as distinctive among hardcovers as the Tower is among man-made structures. Failure recently had the opportunity to ask Shrady a few questions about the Tower, as well as his book's unique binding.
Would you describe the Tower of Pisa as the product of flawed construction?
Most certainly. To begin with, the Tower of Pisa, as well as the other buildings in the so-called Campo dei Miracoli—the cathedral, the baptistery, and the Camposanto cemetery—are all built on what is essentially a former bog. Consequently, the subsoil is forever shifting and prone to flooding. When the architect (who remains unknown) projected the structure he failed to sufficiently account for the unstable terrain, and began to build what would be a 14,700 metric-ton tower of marble and limestone atop a mere three-meter deep foundation. The Tower of Pisa, in other words, was destined to tilt because it was flawed from the outset.
When and why did the Tower come closest to toppling over?
In 1838, a local architect named Alessandro della Gherardesca thought that it would be wise to excavate a catino [walkway] around the base. Workers promptly hit a subterranean water channel, the whole base of the campanile flooded, and the structure began to tilt anew after centuries of relative stability. The incident serves to illustrate a recurring theme—that is, most of those who have professed to want to “save” or “improve” the Tower of Pisa have been those who have come closest to toppling it.
What made the 1934 attempt to stabilize the Tower so disastrous?
To the Italian Fascists, the Tower of Pisa was an inappropriate symbol for a nation with imperial designs, and Mussolini ordered it shored up and stabilized. Not surprisingly, the remedy proved as brutal as Fascist politics—361 holes were bored into the foundation and pumped full with 90 tons of cement. The measure again shattered the Tower's hard-found equilibrium, but no one dared protest. As it happens, Mussolini owned the cement factory.
What happened on September 6, 1995?
Among engineers and architects involved in the most recent restoration the date has become known as Black September. In the midst of works to install underground cables to anchor the campanile the structure suddenly lurched four millimeters to the south. The distance may appear a trifle, but in fact, it was theoretically enough to push the Tower over the edge.
Prior to the most recent intervention what factors contributed to the Tower's risk of collapse?
Undoubtedly the shifting terrain but also the structural stress on the deteriorating stone and marble. The Tower was less at risk of cleanly falling over than of buckling at points where the pressure was greatest and the stone weakest.
Did Galileo [Galilei] ever conduct experiments from atop the Tower or is that a myth?
There is no hard evidence to support the almost universally held claim. The myth first emerged as a result of the overripe imagination of Galileo's secretary and first biographer, Vincenzo Viviani. The image of Galileo atop the Tower proved so compelling that nearly every subsequent biographer incorporated the myth, in various guises, as a pivotal event in the life of the scientist, and indeed, the whole history of modern science.
By what method was the Tower stabilized in the 1990s?
By a method known as soil extraction, or soil subsidence, in which earth was excavated from beneath the foundation on the north side in order to gently coax the structure back toward the perpendicular.
As of today, what is the long-term prognosis for the Tower?
Engineers responsible for the successful restoration effort estimate that the Tower will be stable for another 300 years, but bear in mind too that natural causes such as an earthquake (and Pisa is in a region of considerable seismic activity), could do in the Tower in an instant.
Tell me about the decision to skew the cover and pages of the book.
First of all, let me apologize for the havoc the book wreaks on ones bookshelf! However, the book, like the Tower, does manage to stand on its own, if just. The skewed format was the idea of the designers and marketing department at Simon & Schuster. In any other instance, I would have thought the idea preposterous, but for a book on the Leaning Tower of Pisa, it reminds one just how skewed things can be.