1 00:00:00,120 --> 00:00:02,639 Speaker 1: This Day in History Class is a production of iHeartRadio. 2 00:00:04,280 --> 00:00:08,280 Speaker 1: Hello and welcome to This Day in History Class, a 3 00:00:08,360 --> 00:00:12,200 Speaker 1: show that explores the ups, downs, and in betweens of 4 00:00:12,240 --> 00:00:17,320 Speaker 1: everyday history. I'm Gay Bluesia and today we're talking about 5 00:00:17,360 --> 00:00:21,040 Speaker 1: how the Leaning Tower of Pisa got its trademark lean 6 00:00:21,560 --> 00:00:24,119 Speaker 1: and why it took more than six hundred years for 7 00:00:24,239 --> 00:00:33,840 Speaker 1: engineers to finally get a grip on it. The day 8 00:00:34,240 --> 00:00:39,599 Speaker 1: was February twenty seventh, nineteen sixty four. The Italian government 9 00:00:39,720 --> 00:00:43,640 Speaker 1: began accepting proposals for how to save the Leaning Tower 10 00:00:43,680 --> 00:00:47,400 Speaker 1: of Pisa from collapsing. At the time, the top of 11 00:00:47,440 --> 00:00:51,400 Speaker 1: the eight story tower was leaning seventeen feet south of 12 00:00:51,479 --> 00:00:54,520 Speaker 1: its base, and the tilt was getting worse by a 13 00:00:54,560 --> 00:00:58,240 Speaker 1: fraction of an inch every year. Officials worried that the 14 00:00:58,480 --> 00:01:02,640 Speaker 1: iconic tower might in the next few decades or even 15 00:01:02,760 --> 00:01:06,240 Speaker 1: sooner if there was an earthquake or a powerful storm. 16 00:01:06,360 --> 00:01:10,000 Speaker 1: All of Italy's previous attempts to correct the problem had failed, 17 00:01:10,240 --> 00:01:14,240 Speaker 1: so the country decided to seek suggestions from the international community. 18 00:01:14,880 --> 00:01:17,840 Speaker 1: Experts from all over the world weighed in on how 19 00:01:17,880 --> 00:01:21,560 Speaker 1: to save one of Italy's most popular landmarks, but despite 20 00:01:21,560 --> 00:01:25,360 Speaker 1: some promising ideas. They didn't land on a winning strategy 21 00:01:25,640 --> 00:01:30,199 Speaker 1: until thirty five years later. Work on the tower began 22 00:01:30,400 --> 00:01:33,760 Speaker 1: in eleven seventy three as part of the construction of 23 00:01:33,880 --> 00:01:38,600 Speaker 1: PISA's Grand Cathedral complex. At the time, Pisa was a 24 00:01:38,640 --> 00:01:42,160 Speaker 1: major trading power and one of the wealthiest cities in Europe. 25 00:01:42,640 --> 00:01:45,360 Speaker 1: To celebrate that good fortune and to show it off 26 00:01:45,400 --> 00:01:48,760 Speaker 1: a bit, the city started building a lavish town square 27 00:01:48,800 --> 00:01:52,720 Speaker 1: on the northwestern edge of the city. That complex, known 28 00:01:52,760 --> 00:01:57,000 Speaker 1: today as the Piazza de Miracoli or the Square of Miracles, 29 00:01:57,320 --> 00:02:00,760 Speaker 1: was designed to hold three structures central to religious life. 30 00:02:01,240 --> 00:02:05,800 Speaker 1: A baptistery to represent birth, a cathedral to represent life, 31 00:02:06,040 --> 00:02:10,240 Speaker 1: and a cemetery to represent death. In addition, there would 32 00:02:10,240 --> 00:02:14,160 Speaker 1: be the Tower of Pisa, a freestanding white marble tower 33 00:02:14,360 --> 00:02:18,120 Speaker 1: that would house the bells of the cathedral. Although ornate 34 00:02:18,240 --> 00:02:20,680 Speaker 1: in its own right, the tower wasn't meant to be 35 00:02:20,760 --> 00:02:24,440 Speaker 1: any more alluring or unique than the neighboring structures, But 36 00:02:24,560 --> 00:02:27,520 Speaker 1: thanks to an engineering mishap, it became one of the 37 00:02:27,520 --> 00:02:31,040 Speaker 1: most famous buildings in the world, although not for the 38 00:02:31,080 --> 00:02:35,120 Speaker 1: reason that architects would have wanted. It took the builders 39 00:02:35,280 --> 00:02:38,920 Speaker 1: five years to complete two of the tower's eight stories, 40 00:02:39,160 --> 00:02:42,320 Speaker 1: and by then things were already looking a bit wonky. 41 00:02:42,880 --> 00:02:46,480 Speaker 1: The tower's foundation had begun to settle unevenly, and as 42 00:02:46,560 --> 00:02:50,280 Speaker 1: a result, the whole structure had started tilting towards the south. 43 00:02:51,240 --> 00:02:54,760 Speaker 1: The reason for the tower's precipitous lean is now believed 44 00:02:54,760 --> 00:02:57,000 Speaker 1: to be the very site on which it was built. 45 00:02:57,480 --> 00:03:00,720 Speaker 1: The city of Pisa lies right between the Arnau and 46 00:03:00,880 --> 00:03:04,919 Speaker 1: Sercio rivers in Tuscany, and the tower itself was built 47 00:03:04,960 --> 00:03:08,520 Speaker 1: not far from the shore of the Ligurian Sea. As 48 00:03:08,560 --> 00:03:11,520 Speaker 1: a result of the area's high water table, the ground 49 00:03:11,600 --> 00:03:15,280 Speaker 1: beneath the tower was a watery mix of clay, shells 50 00:03:15,360 --> 00:03:18,440 Speaker 1: and sand, not an ideal place to put a tall, 51 00:03:18,560 --> 00:03:23,040 Speaker 1: heavy building. Soon after the problem was discovered, war broke 52 00:03:23,080 --> 00:03:26,840 Speaker 1: out between Pisa and its fellow Italian city states Lucca 53 00:03:27,080 --> 00:03:31,160 Speaker 1: and Florence. The conflicts halted construction on the tower for 54 00:03:31,240 --> 00:03:34,000 Speaker 1: nearly a century, but the delay turned out to be 55 00:03:34,040 --> 00:03:36,680 Speaker 1: a good thing, as it allowed the Bell Tower's foundation 56 00:03:36,840 --> 00:03:40,960 Speaker 1: to settle, further, limiting the risk of its collapse. Work 57 00:03:41,000 --> 00:03:44,480 Speaker 1: on the tower eventually resumed in fits and starts, and 58 00:03:44,560 --> 00:03:48,920 Speaker 1: builders made several efforts to mitigate the tower's lean. For instance, 59 00:03:49,080 --> 00:03:52,240 Speaker 1: While working on the eighth floor, they angled the story 60 00:03:52,280 --> 00:03:54,920 Speaker 1: to the north to try to balance out the structure's 61 00:03:54,960 --> 00:03:59,560 Speaker 1: southern drift. Unfortunately, the tactic failed, as the added weight 62 00:03:59,600 --> 00:04:01,960 Speaker 1: at the tip up still caused the tower to lean 63 00:04:02,040 --> 00:04:06,560 Speaker 1: even farther. Having done everything they could, the builders completed 64 00:04:06,560 --> 00:04:10,400 Speaker 1: the tower around thirteen seventy. That means it took just 65 00:04:10,560 --> 00:04:13,600 Speaker 1: under two centuries to build it from start to finish, 66 00:04:13,840 --> 00:04:17,400 Speaker 1: though the actual working period was only about twenty years. 67 00:04:18,160 --> 00:04:21,559 Speaker 1: Over the next six centuries, the tower continued to sink 68 00:04:21,600 --> 00:04:25,080 Speaker 1: at an annual rate of point zero five inches or 69 00:04:25,279 --> 00:04:29,279 Speaker 1: one point two seven millimeters. The lean gradually became more 70 00:04:29,360 --> 00:04:33,719 Speaker 1: and more noticeable, until finally it was the structure's defining feature, 71 00:04:33,960 --> 00:04:36,080 Speaker 1: and a reference to it was even added to the 72 00:04:36,080 --> 00:04:40,719 Speaker 1: tower's name. By nineteen sixty four, the Leaning Tower of 73 00:04:40,839 --> 00:04:44,520 Speaker 1: Pisa was one of the most visited tourist attractions in Italy, 74 00:04:44,800 --> 00:04:48,120 Speaker 1: with millions of people flocking to the Square of Miracles 75 00:04:48,160 --> 00:04:51,880 Speaker 1: each year to see it. The tower's popularity gave a 76 00:04:51,920 --> 00:04:56,200 Speaker 1: reliable boost to the city's economy, but its growing instability 77 00:04:56,360 --> 00:04:59,719 Speaker 1: was beginning to make the government nervous. By that point, 78 00:04:59,800 --> 00:05:02,320 Speaker 1: the top of the one hundred and eighty foot tower 79 00:05:02,520 --> 00:05:05,880 Speaker 1: was roughly seventeen feet out of alignment with its base. 80 00:05:06,440 --> 00:05:09,800 Speaker 1: Experts warned that it could easily topple in the right conditions, 81 00:05:09,960 --> 00:05:12,960 Speaker 1: and the longer the issue went unaddressed, the more likely 82 00:05:13,000 --> 00:05:16,880 Speaker 1: it was to end in tragedy, and so. On February 83 00:05:16,920 --> 00:05:21,280 Speaker 1: twenty seventh, nineteen sixty four, the Italian government began welcoming 84 00:05:21,320 --> 00:05:26,520 Speaker 1: suggestions for how to stabilize its beloved monument. A multinational 85 00:05:26,560 --> 00:05:31,400 Speaker 1: committee of historians, engineers, and mathematicians was convened to discuss 86 00:05:31,440 --> 00:05:35,560 Speaker 1: possible solutions. The most promising plan was to drill holes 87 00:05:35,600 --> 00:05:39,200 Speaker 1: into the tower's foundation and pour a concrete ring around 88 00:05:39,240 --> 00:05:43,640 Speaker 1: its base to stop the structure from sinking any deeper. Unfortunately, 89 00:05:43,839 --> 00:05:47,160 Speaker 1: when this was attempted in nineteen sixty six, the drilling 90 00:05:47,279 --> 00:05:50,600 Speaker 1: promptly caused the lean to increase, and the project had 91 00:05:50,600 --> 00:05:54,120 Speaker 1: to be aborted. Several more attempts were made in the 92 00:05:54,160 --> 00:05:58,520 Speaker 1: following decades, including wrapping plastic coated steel pieces around the 93 00:05:58,560 --> 00:06:03,039 Speaker 1: tower's lower floors and installing anchored cable counterweights on its 94 00:06:03,040 --> 00:06:07,600 Speaker 1: north side. However, none of those methods proved viable, as 95 00:06:07,600 --> 00:06:10,760 Speaker 1: the government didn't want to make permanent additions to the building, 96 00:06:11,000 --> 00:06:15,359 Speaker 1: such as unsightly braces or cables. The tower had remained 97 00:06:15,400 --> 00:06:19,000 Speaker 1: open to visitors throughout the various restoration attempts, but in 98 00:06:19,080 --> 00:06:22,200 Speaker 1: nineteen ninety the decision was made to close the monument 99 00:06:22,400 --> 00:06:26,760 Speaker 1: due to heightened safety concerns. Once again, the Italian government 100 00:06:26,920 --> 00:06:31,640 Speaker 1: organized an international task force, and once again multiple proposals 101 00:06:31,640 --> 00:06:36,760 Speaker 1: were put forward, considered, and ultimately rejected. Finally, in nineteen 102 00:06:36,880 --> 00:06:40,080 Speaker 1: ninety nine, the panel of experts hit upon a solution 103 00:06:40,320 --> 00:06:44,800 Speaker 1: that seemed promising and satisfied all of Italy's conditions. They 104 00:06:44,880 --> 00:06:48,520 Speaker 1: determined that if enough soil was carefully excavated from the 105 00:06:48,600 --> 00:06:52,240 Speaker 1: tower's elevated north side, the building would settle into the 106 00:06:52,279 --> 00:06:56,000 Speaker 1: newly formed space and the tilt would be reduced. The 107 00:06:56,040 --> 00:07:00,280 Speaker 1: only cash was that this process, known as under excavation, 108 00:07:00,760 --> 00:07:04,360 Speaker 1: ran the risk of disturbing the tower's foundation, which could 109 00:07:04,400 --> 00:07:07,800 Speaker 1: cause it to collapse. To avoid this, the engineers had 110 00:07:07,800 --> 00:07:11,679 Speaker 1: to work extremely slowly, removing no more than a gallon 111 00:07:11,760 --> 00:07:15,160 Speaker 1: or two of soil in a day. As a further precaution, 112 00:07:15,480 --> 00:07:19,080 Speaker 1: they temporarily attached a massive cable harness to the tower, 113 00:07:19,280 --> 00:07:22,000 Speaker 1: which would hopefully keep it standing in the event of 114 00:07:22,040 --> 00:07:28,000 Speaker 1: a sudden destabilization. The soil extraction proceeded slowly, but strong 115 00:07:28,120 --> 00:07:31,880 Speaker 1: progress was evident along the way. Within six months, the 116 00:07:31,920 --> 00:07:34,480 Speaker 1: tilt had been reduced by more than an inch, and 117 00:07:34,520 --> 00:07:36,800 Speaker 1: by the end of the year two thousand by nearly 118 00:07:36,800 --> 00:07:40,200 Speaker 1: a foot. The project wrapped up in late two thousand 119 00:07:40,200 --> 00:07:44,000 Speaker 1: and one, after thirty eight cubic meters or about thirteen 120 00:07:44,080 --> 00:07:48,280 Speaker 1: hundred cubic feet of soil had been removed. The Leaning 121 00:07:48,320 --> 00:07:51,520 Speaker 1: Tower of Pisa was still leaning when it reopened to 122 00:07:51,520 --> 00:07:54,960 Speaker 1: the public that December, but thanks to the controlled excavation, 123 00:07:55,360 --> 00:07:57,920 Speaker 1: its tilt had been reduced by a full foot and 124 00:07:57,920 --> 00:08:01,360 Speaker 1: a half. The good news can continued in two thousand 125 00:08:01,400 --> 00:08:04,520 Speaker 1: and eight, when an inspection confirmed that the tower's movement 126 00:08:04,720 --> 00:08:07,600 Speaker 1: had indeed stopped for the first time since it had 127 00:08:07,640 --> 00:08:12,040 Speaker 1: been built. Experts say that the eighteen inches of verticality 128 00:08:12,160 --> 00:08:16,320 Speaker 1: reclaimed through under excavation will give the landmark another two 129 00:08:16,400 --> 00:08:20,240 Speaker 1: to three centuries of life. The biggest threat to the 130 00:08:20,280 --> 00:08:24,520 Speaker 1: tower's longevity would be an unpredictable disaster such as an earthquake, 131 00:08:24,920 --> 00:08:28,240 Speaker 1: but even in that case, there's a surprisingly good chance 132 00:08:28,280 --> 00:08:32,480 Speaker 1: that it might survive. That's because, according to engineers, the 133 00:08:32,559 --> 00:08:36,400 Speaker 1: Leaning Tower of Pisa benefits from a phenomenon known as 134 00:08:36,559 --> 00:08:42,160 Speaker 1: dynamic soil structure interaction. It basically means that during an earthquake, 135 00:08:42,400 --> 00:08:45,240 Speaker 1: the tower wouldn't move and shake like a building with 136 00:08:45,280 --> 00:08:48,480 Speaker 1: a firmer foundation, because its soft soil would have a 137 00:08:48,520 --> 00:08:52,520 Speaker 1: cushioning effect. So ironically, the very thing that caused the 138 00:08:52,559 --> 00:08:55,319 Speaker 1: tower to lean in the first place is also its 139 00:08:55,360 --> 00:08:59,720 Speaker 1: best bet forwithstanding a seismic event. Still, if the leaning 140 00:08:59,760 --> 00:09:03,200 Speaker 1: Tower of Pisa should ever fall, it's worth noting that 141 00:09:03,240 --> 00:09:06,679 Speaker 1: the city does have a backup too. In fact, the 142 00:09:06,679 --> 00:09:10,440 Speaker 1: bell towers of two other nearby churches have also failed 143 00:09:10,440 --> 00:09:13,560 Speaker 1: to stand up straight, and while their leans aren't nearly 144 00:09:13,600 --> 00:09:16,600 Speaker 1: as drastic, they could still make for a decent selfie 145 00:09:16,800 --> 00:09:23,079 Speaker 1: in a pinch. I'm Gabe Lucia and hopefully you now 146 00:09:23,160 --> 00:09:26,760 Speaker 1: know a little more about history today than you did yesterday. 147 00:09:27,600 --> 00:09:29,400 Speaker 1: If you'd like to keep up with the show, you 148 00:09:29,440 --> 00:09:33,319 Speaker 1: can follow us on Twitter, Facebook, and Instagram at TDI 149 00:09:33,880 --> 00:09:37,439 Speaker 1: HC Show, and if you have any feedback to share, 150 00:09:37,720 --> 00:09:40,120 Speaker 1: feel free to pass it along by writing to this 151 00:09:40,320 --> 00:09:44,800 Speaker 1: Day at iHeartMedia dot com. Thanks to Chandler Mays for 152 00:09:44,880 --> 00:09:47,640 Speaker 1: producing the show, and thanks to you for listening. I'll 153 00:09:47,640 --> 00:09:50,880 Speaker 1: see you back here again tomorrow for another day in 154 00:09:51,120 --> 00:10:01,240 Speaker 1: history class at the Future