Roughly midday to 2pm, especially on a Sunday, central Madrid runs on vermouth — a century-old pre-lunch ritual that's seen a genuine local revival in recent years.
La hora del vermut is a pre-lunch aperitif tradition — a small glass of vermouth, ideally on tap ("de grifo"), taken with friends or family before Sunday lunch, which in Madrid rarely starts before 2:30pm. The idea, traditionally, was that the bittersweet, herb-fortified wine would "wake up" the appetite ahead of the meal. It became especially popular during the Franco era, as working and lower-middle-class families gathered at neighbourhood bars after Sunday mass, and has stayed a deeply rooted social habit ever since.
Ask for "un vermut de grifo" — vermouth from the tap, rather than the bottle — and it'll typically arrive over ice with an orange slice and an olive. Red vermouth (vermut rojo), sweeter and spiced, is the dominant style in Madrid, though a drier white version exists too. Some locals order it "con sifón," lengthened with a splash of soda water from a classic siphon bottle, for a lighter drink.
Salty, acidic snacks that stand up to the vermouth's bittersweet profile: olives, boquerones en vinagre (vinegar-cured anchovies), patatas bravas, or a simple tortilla de patatas.
La Latina, Malasaña and the Barrio de las Letras have the highest concentration of old-school bodegas serving vermouth this way — look for "vermut de grifo" painted on the window rather than a cocktail-bar aesthetic. It's a tradition best experienced at an old, tiled, unglamorous bar, not a designed-for-Instagram one.
Sunday, between roughly noon and 2pm, is when the ritual is at its fullest — though plenty of bars now pour vermouth on tap any day, any hour.