The Leaning Tower of Pisa is the campanile, or freestanding bell tower of the cathedral of the Italian city of Pisa. Although, intended to stand vertically, the tower began leaning to the southeast soon after the onset of construction in 1173 due to a poorly laid foundation and loose substrate that has allowed the foundation to shift direction. Its weight is estimated at 14,500 tons and has 296 or 294 steps.
The Tower of Pisa was a work of art, performed in three stages over a period of about 177 years. Construction of the first floor of the white marble campanile began on August 9, 1173, a period of military success and prosperity. The first floor is surrounded by pillars with classical capitals, leaning against blind arches. The tower began to sink after construction progressed to the third floor in 1778. This was due to a mere three-meter foundation, set in weak, unstable subsoil. This means the design was flawed from the beginning.
Construction was subsequently halted for almost a century because the Pisans were almost continually engaged in battles with Genoa, Lucca and Florence. This allowed time for the underlying soil to settle. Otherwise, the tower would almost certainly have toppled. In 1272, construction resumed and in an effort to compensate for the tilt, engineers built higher floors with one side taller than the other. This made the tower begin to lean in the other direction.
