On this day, 852 years ago, on August 9, 1173 (June 29, 1173, the famous Leaning Tower of Pisa in Italy broke ground. The construction of the Bell Tower of Pisa Cathedral began in August 1173. The project took two long breaks and took about 200 years to complete. When construction began on August 9, 1173, the design was vertical. The original design was 8 stories and 54.8 meters high. Its unique white shining medieval building will be the most noteworthy in Europe even if it is not tilted later. One of the bell towers. In 1185, when the bell tower was built to the fourth floor, it was discovered that due to uneven foundation and soft soil layers, the bell tower had tilted to the southeast, so the project was suspended. In 1198, the existence of ringing bells in the bell tower was recorded, which marked that although the bell tower was tilted, at least one ringing bell was hung, realizing its original intention as a bell tower. In 1231, the project continued, and for the first time, marble was recorded in the Bell Tower. The builders took various measures to correct the tilt, deliberately tilting the upper floor of the bell tower in the opposite direction to compensate for the deviation of the center of gravity that had occurred. When it reached the seventh floor in 1278, the tower body was no longer straight, but concave. The project was suspended again. In 1292, GiovanniPisano used a plumb line to measure the tilt of the clock tower. In 1360, after almost a century of stagnation, the Bell Tower made its final sprint towards completion and made its last important revision. In 1372, the top floor where the clocks were placed was completed. The 54-meter-high eight-story clock tower has a total of 7 bells, but it has never sounded because the clock tower is in danger of collapsing at all times.