La Casa del Abuelo

A century-old institution built on a single dish done better than almost anywhere else — gambas al ajillo, sizzling shrimp in garlic and chilli oil, served with bread for mopping up what's left. A sweet house wine (vino de la casa) is the traditional pairing.

The original Calle Victoria location is tiny and stand-up only; several newer branches around the city offer seating if that matters more than the historic room. Order the gambas al ajillo and the gambas a la plancha together to compare the two preparations — regulars rarely order just one. Expect a short wait at peak times, but turnover is fast since it's built for quick, standing tapas rather than lingering.