In the 1990's the "Leaning Tower of Pisa" was finally reopened to the public, after having been closed for several years. During that time, engineers completed a 25 million dollar renovation project designed to stabilize the tower. They removed 110 tons of dirt, and reduced its famous lean by about sixteen inches. Why was this necessary? Because the tower has been tilting further and further away from vertical for hundreds of years, to the point that the top of the 185-foot tower was seventeen feet further south than the bottom, and Italian authorities were concerned that if nothing was done, it would soon collapse. What was the problem? Bad design?  Poor workmanship? An inferior grade of marble? No. The problem was what was underneath. The tower was built on the shifting sands of a former estuary.  The soil was not stable enough to support a monument of this size. The tower had no firm foundation.

You may not know this but the Tower is simply the bell tower of the local church cathedral. A fitting reminder for that cathedral that building on sand will incur great cost.