The Museo del Pisco is less a museum than an excellent bar with a teaching component. Half the front room is a tasting counter where staff will pour you a flight of single-grape piscos (quebranta, italia, torontel, mosto verde) and explain what makes each one distinct. Half is the cocktail bar proper, mixing chilcanos, pisco sours, and a regularly changing list of original drinks. The atmosphere is candlelit and unhurried.
It is a useful first stop for anyone planning to drink their way around southern Peru — the staff are genuinely good at picking out what you'll like and pointing you to the producers worth seeking out. There's also a small food menu, mostly Peruvian small plates designed to go with the drinks.