<P> The height of the tower is 55.86 metres (183.27 feet) from the ground on the low side and 56.67 metres (185.93 feet) on the high side . The width of the walls at the base is 2.44 m (8 ft 0.06 in). Its weight is estimated at 14,500 metric tons (16,000 short tons). The tower has 296 or 294 steps; the seventh floor has two fewer steps on the north - facing staircase . Prior to restoration work performed between 1990 and 2001, the tower leaned at an angle of 5.5 degrees, but the tower now leans at about 3.99 degrees . This means the top of the tower is displaced horizontally 3.9 metres (12 ft 10 in) from the centre . </P> <P> There has been controversy about the real identity of the architect of the Leaning Tower of Pisa . For many years, the design was attributed to Guglielmo and Bonanno Pisano, a well - known 12th - century resident artist of Pisa, famous for his bronze casting, particularly in the Pisa Duomo . Pisano left Pisa in 1185 for Monreale, Sicily, only to come back and die in his home town . A piece of cast bearing his name was discovered at the foot of the tower in 1820, but this may be related to the bronze door in the façade of the cathedral that was destroyed in 1595 . A 2001 study seems to indicate Diotisalvi was the original architect, due to the time of construction and affinity with other Diotisalvi works, notably the bell tower of San Nicola and the Baptistery, both in Pisa . </P> <P> Construction of the tower occurred in three stages over 199 years . Work on the ground floor of the white marble campanile began on August 14, 1173 during a period of military success and prosperity . This ground floor is a blind arcade articulated by engaged columns with classical Corinthian capitals . </P> <P> The tower began to sink after construction had progressed to the second floor in 1178 . This was due to a mere three - metre foundation, set in weak, unstable subsoil, a design that was flawed from the beginning . Construction was subsequently halted for almost a century, because the Republic of Pisa was 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 1198, clocks were temporarily installed on the third floor of the unfinished construction . </P>

When did they start building the leaning tower of pisa