The woman, in her 80s, was reportedly upset at the way the fresco had deteriorated and took it on herself to restore the image.
BBC Europe correspondent Christian Fraser says the delicate brush strokes of Elias Garcia Martinez have been buried under a haphazard splattering of paint.
The once-dignified portrait now resembles a crayon sketch of a very hairy monkey in an ill-fitting tunic, he says.
http://www.bbc.co.uk/news/world-europe-19349921