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Friday, April 25, 2014

An Architect's Worst Nightmare

Pisa's Piazza del Duomo at sunrise.
His name was Diotisalvi, and you have to feel at least a little sorry for the man. It was the twelfth century, the city was Pisa, Italy, and he was the closest thing they had to a bonafide architect. Moreover, the man had at least three projects going at once and none of them were going well. Work nearby on his Church of Santo Sepolcro was almost complete, but the bell tower was going much too slowly. There were foundation problems with St. John's Baptistery in front of the Pisa Cathedral; but worst of all, out back of the cathedral, there was the campanile. That's what was keeping him awake at nights. Work on the second floor had hardly begun and already there were signs the whole structure was starting to lean. The bell tower would eventually rise eight stories (183 feet) into the air. The lean would only get worse when finished, if indeed, the whole thing didn't topple over with the first strong breeze even before then. The problem was becoming ever more apparent to Diotisalvi, if to no one else. Pisa was a terrible place to build heavy stone structures (especially tall ones). The sandy soil was unstable. The problem with the baptistery was relatively minor. He could fix that, but the bell tower... The ground on the north side was firmer than that on the south side. Tons of stone and tons of money had already been spent. He couldn't just move the whole thing. And even if he could, who's to say a new location would be any better? What's an architect to do? History tells us what Diotisalvi did was to die. In Italian his name means "God save you," which apparently, He did.

The Pisa "Prato dei Miracoli" (Meadow of Miracles) as seen by the French artist, Charles Louis Clerisseau, in 1757. The baptistery is to the left. Artists have long tended to exaggerate the tower's lean slightly in their renderings.
There's no record as to when Diotisalvi was born nor precisely when he died (sometime after 1178). About that time, work was halted on the misbegotten bell tower for almost a hundred years while the city-state of Pisa licked its wounds following several military defeats meted out by its Italian neighbors, Genoa, Lucca, and Florence. This allowed the unfinished pile of cut marble to settle somewhat, righting itself enough to allow architect Giovanni di Simone (who hadn't even been born when the tower was begun), to try to correct the problem. His "solution" was mostly cosmetic. He built the remaining stories taller on the low side, shorter on the high side, thus, in effect, causing the building to curve slightly. Visually, it's largely imperceptible and structurally had little effect. The bell tower continued to lean.

Inside the campanile, seven bells for seven musical notes.
In 1294, with six stories tilting into the sky, construction was once more halted as Pisa once more fought with Genoa...and lost. It wasn't until 1319 that yet another architect, Tommaso di Andrea Pisano was able to top off the seventh floor followed by the Gothic bell housing on the eighth floor in 1372. Seven bells were installed, one for each note on the musical scale. The story of the astronomer, Galileo, dropping cannonballs from the top of the tower in a scientific experiment seems to have been a fabrication by his secretary. It probably never happen. But the story of how a U.S. Army Sergeant saved the troubled tower from an artillery bombardment by the Allies to take out a lofty German observation post did happen. Impressed by the beauty of the tower and cathedral, "saving" it was easy. He simply did nothing. The Germans and the tower survived.

Today, the tower leans at around four degrees, about the same angle as in 1838
(though you'd never guess it from this horrifying 1830 color etching).

The solution looks simple and logical
enough, but took 26 years to devise.
After the war, as Italy once more struggled to pull itself together following yet another military defeat, the tower's survival gradually became ever more problematical. The lean had reached a treacherous 5.5 degrees. The tower was some three feet taller on the north side than the south. If, for no other reason than to save a valuable tourist attraction, something had to be done. Italy called upon the world's best engineering minds to come up with a solution. Actually they got more than they bargained for, from the sublime (800 tons of lead to counterbalance on the north side) to the ridiculous (helium balloons moored overhead to keep the structure from falling over). They tried the lead weights (still in place today) but to little effect. They removed the bells lessening weight at the top. Still the lean not only remained, but continued to grow worse.

Only in seeing the entrance to the tower can one accurately judge the extent to which the tower tilted over the centuries and the massive effort to make it right (almost).
Having straightened up the place somewhat,
 they decided to clean it up too.
Finally, in 1990, more than twenty-five years after they began to study the problem, work began on righting the Leaning Tower of Pisa. Cables were looped around the third level then anchored a good distance away while engineers drilled diagonally under the north foundation to remove more than 38 cubic meters of soil, which slowly nudged the tilting tower back to 3.99 degrees. They could have actually reset it upright, but why waste a perfectly good tourist attraction? The tower was reopened to tourists in December, 2001, about eight months after my wife visited the area. (I chose to visit Florence instead).

Pisa's "Meadow of Miracles" according to Google. The baptistery is at left (the dome being restored), the cathedral in the middle, the campanile to the right, with tourists everywhere in between. My wife's the one about halfway between the tower and the cathedral.

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