If it's open, step into the vestibule of this working 1642 convent, push a bell, and a concealed cloistered nun on the other side of a wooden partition will invite you to buy a bag of house-made treats. Place your money in a revolving compartment, and within a couple of minutes it will flip back round with your order on it. The convent is otherwise off limits to visitors.
Convento de las Mercedarias
Arcos de la Frontera