While the Leaning Tower of Pisa’s Piazza dei Miracoli is world-famous, its just-as-leaning Pisan siblings are virtually unknown.
One is the Bell Tower of the Chiesa di San Nicola:
It is half a mile south from the Leaning Tower. It is actually an almost identical twin, albeit attached to its church and with the columnade on the inside.
The other church tower that failed to remain vertical is a few miles to the east, by the Chiesa di San Michele degli Scalzi.
In this case, the whole church is leaning to one side too. Apparently, the builders noticed there was something odd about their work, and completed the bell tower with light bricks instead of the heavy stones they had started with.