look closely at the spidery tree that dominates the center of the painting and you notice something peculiar. Its branches are covered in penises.

There are 25 of them in all, of different shapes and sizes, complete with testicles. They hang from the limbs of the tree like leaves fluttering in the breeze.

The mural dates from the 13th century and is still visible on a wall in the Italian town of Massa Marittima where it was discovered during renovation work four years ago.