The goal wasn't to make it straight. It was to stop it falling over. And part of the solution was to remove the ground beneath it. For centuries, the Leaning Tower of Pisa has been admired for the very thing that threatened its survival. Behind the familiar tourist photographs is an extraordinary engineering challenge: how do you stabilise a leaning building without causing the collapse you are trying to prevent? Construction began in 1173, on weak, compressible ground. The