English: This elevation shows the interesting quandry facing the campanile. The 'Leaning Tower of Pisa' is the one of the most well known monuments in the world. The tower has been leaning since shortly after its initial construction in 1173 due to unstable substrate soils. The circular shape and great height (currently 55.86 m on the lowest side and 56.70 m on the highest) of the campanile were unusual for their time, and the crowning belfry (likely constructed during the 14th century) is stylistically distinct from the rest of the construction. This belfry incorporates a 14 centimeter correction for the inclined axis below. The siting of the campanile within the Piazza del Duomo diverges from the axial alignment of the cathedral and baptistery, and it has been suggested that its placement might have been due to astrological factors.