Tandem is a musty, 30-year-old joint that you think only you know about, where the same group of old guys always hangs out by the door, and there's always a free seat—even on a Saturday night. Although mention this place to your friends and you’ll learn that half of them also think of the lounge-like institution as their secret hideout. The leather armchairs clustered closely together in the back of a bar barely wider than a Barcelona metro car may have seen better days but who cares when the drinks are strong, and won’t cost you a month’s rent. This is the place for a no-fuss classic done right, but also silky-smooth espresso martinis if your tastes are less old-school.