When you visit the Barcelona cathedral you will see 13 geese in the courtyard, it is related to the saint of the city, Saint Eulalia.

Her tomb is located on the cathedral and you can see it, just try not to look inside you will get in serious troubles.

The 13 is related to the age of death that this martyred saint and can see references on the structure of the building, like the door of entry.

Now why the geese I do not know really why this particular animal is kept inside are they easy to maintain or there are symbolic for the golden eggs or some other legend. I do not really know I just that probably related to being loyal and brave animals.