On this day, 07 January 1990, The Leaning Tower of Pisa was closed to the public. The accelerated rate of "leaning" raised fears for the safety of its visitors. The medieval tower took over 200 years to build. The tower reopened in 2001 after stabalization but there were additional stabilization problems.
It is believed that Galileo did an experiment on the tower and discovered gravity. Here is a short NASA video that demonstrates this experiment.
Why do I find this interesting? Despite the problems with this building, look at how long it has stood-- Europeans hadn't found their way to the Americas yet! Think about how many buildings in the New World have NOT stood the test of time and you will realize that the Italian craftsman really did quality work.
For more information:
Tour Italy Now article