Jingū at Isë has a sacred well, from which water is drawn every morning in order to prepare the offerings for the kami. (Actually, there are three, so that there are back-up wells if anything happens to the main one.) This well is supposed to have been brought from Takamanohara, the high plain of heaven, via the Japan Sea coast of Kyoto prefecture. I have to confess that I am not entirely clear on how you are supposed to transport a well. It is contained in a jinja, and according to an article in Jinja Shinpō last week, the well itself is the kami of the jinja.
The well is cleaned once a year, in July, immediately after a major festival. This is done by three priests, who spend the previous night purifying themselves, and then, wearing loincloths, are purified again with salt before entering the well. There, they take some of the water out in a bucket, to serve as seed water, before emptying the rest of the water out of the well. They then clean all the moss and algae that have gathered on the stones over the course of a year, cleaning each stone individually and rinsing them down. Finally, the seed water is returned to the well, and the cleaning is completed.
There is a great emphasis on the purity of the priests involved in this task, because they are, after all, cleaning the kami. At least, they are doing so in a sense: the kami is the well, but not the water, and probably not the individual stones in the wall, or the empty space that the water normally occupies. Indeed, even given that the kami is the well, it is still not entirely clear what the kami is.
Incidentally, given the outfit for the cleaners, one might wonder what happens if one of the priests chosen is female. However, that is never a problem, because, to the best of my knowledge, Jingū has no female priests. Similarly, the priest training centre at Jingū is, I believe, the only one that does not admit women at all, although the smaller ones sometimes have years where they have no female students. Certainly, in all the pictures I have seen, the only woman is the Saishu, the Tennō’s personal representative. (There are certain matsuri connected with the Grand Renewal in which a young girl plays an important role, but not adult women.) There are miko and female staff at Jingū, but they are not priests.