Blister plasters are the most-forgotten item
Even with broken-in walking shoes, the Albaicín cobblestones and the Alhambra stone paths create friction points that most people don't notice until day two. Pharmacies in Granada sell blister plasters (apósitos para ampollas, or the brand "Compeed"), but finding one when you need it urgently, mid-afternoon in the upper Albaicín, is a different matter. Pack four or five before you leave. They weigh nothing and save the last two days of a trip from misery.