Torre Pendente or The Leaning Tower of Pisa is one of the world's most famous sights, I've been there twice - once as a child and once more recently - I have to say, I seemed to remember it being at more of an angle the first time round! I can't claim to have climbed up it, as I didn't feel the queue or the entrance fee was worth it but despite the huge amount of tourists visiting it and the plethora of kitsch market stalls, I still think that it is a must place to visit.
The question on everyone's lips is how did it end up at such a dodgy angle... well the statue was flawed from the beginning as it was built on soft ground, noticeable by the time they got to the 3rd floor, fortunately the Pisans were at this time involved in battles against neighbouring Lucans, Florence and Saracens in Genoa and the construction was postponed for about 100 years which let the underlying soil toughen up, the remaining construction work was then completed by various engineers and in one case, one side of the building was made taller than the other in an attempt to balance it out but it ended up tilting the other way instead and giving it, it's curved effect!
Quite a masterpiece and an entertaining building, considering the history behind it. The surrounding area with the cathedral (Piazza del Duomo) is also very nice but obviously absolutely bustling with tourists, it is popular for people to have photos with themselves either pushing or leaning the building and 99% of people seem to be doing it - which I found all a bit stupid!