Explanation:

the Leaning Tower of Pisa does not fall because its center of gravity has been carefully kept within its base. ... In short, this is why the Tower of Pisa does not topple over. The Leaning Tower doesn't fall because its center of gravity is carefully kept within its base. The tower of Pisa has been leaning so long -- nearly 840 years -- that it's natural to assume it will defy gravity forever. But the famous structure has been in danger of collapsing almost since its first brick was laid. It began leaning shortly after construction began in 1173.