This is the ubiquitous N0 8 D0 sign that adorns anything even remotely to do with the city of Seville. "Ubiquitous" is not an exaggeration: it's on municipal buildings, on the buses, on police cars, public toilets, possibly tattooed on the mayor, there's no getting away from it.
What could it possibly mean? Well, pull up a chair for a little semiotics lesson. According to my superior guidebook, the explanation is as follows.
The sign means "No me ha dejado", in English, "She has not deserted me", words attributed to Alfonso the Wise (no comment) after the city of Seville remained loyal to him during a dispute with his son Sancho (no information available on the astuteness, or otherwise, of Sancho, but I think we can draw our own conclusions) during the time of the Reconquest.
Here's the fun part. What you might first interpret as a figure 8 is, upon closer inspection, a stylized skein of wool, the Spanish word for which is madeja. Hence No m'a dejado.