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The Leaning Tower of Pisa The leaning tower has never been straight. Not long after work began in 1173, the foundation settled unevenly, and the tower started inclining toward the north. Evidence for this initial incline can be seen in the design of the tower itself: to keep the first few stories level, worker, make the columns and arched of the third story on the sinking northern side just slightly taller than the features on the southern side. Political unrest in Pisa halted construction in 1178, in the middle of work on the fourth level. Work resumed almost 100 years later, in 1272, and by that time, the tower had tilted to the souththe direction it still points today. Again, designer hoped to correct the lean, this time by adjusting the height of the fifth story, making the southern side somewhat taller than the northern side. In 1278, with seven stories completed, work on the tower ceased once again because of political unrest. By 1292, the towers tilt was so obvious that a group of masons were asked to investigate the problemthe first of many commissions to study the tower appointed over the past 700 years. The eighth story and final addition, the bell chamber, was built between 1360 and 1370. Once more, architects attempted to correct for the southward lean, this time by angling the bell chamber northward. These efforts, combined with the slow time scale of construction, have so far prevented the tower from topping(倒塌) over. | 
