The Leaning Tower of Pisa (Torre pendente di Pisa) is the free-standing campanile (bell tower) of the cathedral of Pisa, one of many works of art and architecture in the city’s Piazza del Duomo, also known as Piazza dei Miracoli (Square of Miracles), to the north of the old town center. Intended to stand vertically, the tower began leaning soon after the onset of construction in 1173 due to a poorly laid foundation and loose substrate.