The Leaning Tower of Pisa is the most famous crooked building worldwide. In August 1173 when construction work started nobody could have foreseen that it would come out that way. It was planed to build a detached bell tower. Once the third floor was reached the tower began to slant. After a 100-year construction freeze an adjustment was made in which the next four floors were built skew in order to make a correction. In 1372 the labour work on the bell tower came to an end. Only later they noticed that the subsurface consisted of mud and sand. The towers weight was plainly too heavy for the unstable foundation. After remediation measures in 1998, one hopes that the tower is secured for another 300 years.