Nope.. I've never been to Pisa
I just made the tower striaght and then rotated the picture till the angle of tilt was the same as the original picture with a leaning tower..

Then a crop and a bit of a clone to fill in some sky and bingo - The Straight Tower of leaning Pisa..
( Darryn.R www.themoononline.com, Mon 18 Aug 2003, 10:22, archived)

*applauds*
Top effort that man.
( Ijon Tichy, Mon 18 Aug 2003, 10:41, archived)