The structure was conceived as the cathedral's bell tower. Construction began in 1173 and the tower started leaning soon afterwards due to subsidence of the ground underneath its base. A project to keep the tower from leaning more and tipping over finally reached a successful conclusion in 2001, and the tower is again open to those wishing to climb it. Climbing the tower requires a reservation-based ticket for €18. Tickets can be bought for the tower on the day, for a specific entry time. This could be 45 min-2 hr after the purchase time, but there is a lot to see while you wait. It is better if you buy tickets online for €18 well in advance (up to 20 days). The tickets are non-exchangeable, effectively non-refundable, and only good for the tower, so they're a bit of a risk to purchase in advance. Make the effort to climb, though, and you'll be rewarded by the view. The famous Pisa leaning tower is not the only one, due of the marshy land that they are built on, there are other 2 towers in Pisa: the Bell Tower of 43.7167510.396741 San Nicola Church , near the banks of Arno and the Bell Tower of 43.70595610.4191981 San Michele of Scalzi Church . For safety reasons, children who will not have turned 8 by the end of this year are not permitted to enter. Under-18s must be accompanied by an adult. ID may be requested to certify the age.