Town Tavern Washington, DC and Metromix are hosting a special Four Square party next Saturday, March 13. For the uninitiated, Foursquare is a phone app that gives you and your friends a new way of exploring your city. When you “check in” at different places, you earn points and unlock badges for discovering new things around town. The Swarm Badge (which is apparently the most difficult to achieve) will be awarded on Saturday if 50 or more guests attend. Not interested? They’ll have free beer. That’s right. Click the link and RSVP.