Construction of the cathedral of Pisa's campanile began in 1173, but after only 5 years (they were working on the third floor at that point) the tower began sinking due to shallow foundations and unstable soil. It took nearly 200 years to complete the tower, both because architects were trying to figure out a way to make the tower stand and also because the city was frequently involved in battles against the cities of Florence, Genoa and Lucca. The tower was officially completed with the addition of the bell chamber in 1372. At that time, the tower was already leaning by about 1.5 m and it kept on sinking until major works were undertaken in the 1990s to stabilize the structure.
The tower is now leaning by about 4 m and, since 2001, visitors are once more allowed to climb to the top. My first impressions of the tower were that its Romanesque architecture was truly beautiful, something that is often overlooked in favour of its more obvious characteristics, and that it was much more tilted than I imagined it to be! Climbing the tower's circular stairs is a bit of an experience in itself since it's almost like climbing up a boat that's rocking back and forth.
The view of the city, the Piazza dei Miracoli, and the surrounding countryside was amazing.