Ten things you never knew about the Leaning Tower of Pisa ..

1. It used to lean the other way.
2. It is now banana - shaped.
3. The top is straighter than the base.
4. I've had enough of this.

It was clear shortly after building started (in 1173) that the fine river soils of the Pisan Plain were collapsing under the tower's weight.

At just three stories high the tower slumped; building continued with irregular-shaped stonework in an attempt to counterbalance this, and, voila, the tower slumped in the opposite direction!
As work continued, the ongoing vertical compensation has resulted in the slight banana shape seen today. The final layer, the bell chamber itself, was finished in 1350, and was built truer to the perpendicular than the rest of the tower.

The tower has been closed to the public since 1990. However, largely thanks to the work of an English engineer, the tower is as stable as it has been in 80 years and is now re-opened to the public.