Convento de San Leandro
Inside a quiet foyer strewn with potted plants is a heavy-set wooden door with bolted gold trim and a small, revolving turnstile tray. Behind that door is a convent, a practicing order of nuns in existence since 1295 that sell just one item, Yemas de San Leandro, a sweet treat made with egg yolk, lemon juice, and sugar. Take note of the price list on the wall, place your money on the tray, rotate, and wait. Minutes later a box of yemas will magically appear without so much as a glimpse of the cloistered nun on the opposite side.