This is found in the SE Boston Common area. The building itself is unmarked and you have to enter a red door to explore the area. The building has no notable loot but has an interesting history instead. It seems that the guests and patrons of the club has committed mass suicide right before the world ended. This is the only place in the game where you can find the Poisoned Wine item.
The club's terminal is Novice-locked. There's an Expert wall safe in the room behind the bar counter. You can open the safe by successfully hacking the terminal.