Today is National Root Beer Float Day, and if you head to an A&W location (the closest ones to the city are in Capitol Heights and Upper Marlboro) you can pick up a free float for the rest of the day.
Allow me to offer a dissenting opinion here: A root beer float is the result of two stellar components producing something less than the sum of its parts. There's perhaps a two-minute window when a root beer float is satisfying, when the ice cream is still sufficiently dense and the root beer is still fizzy. Beyond that, you're in the danger zone, when half-melted ice cream turns the root beer into a flat, taupe slurry that's as much fun to finish as your leftover morning coffee.
You want a float that's worth a trip? Make for the Maple Ave Restaurant and order the beer float, which pairs vanilla ice cream with DC Brau's Penn Quarter Porter. The sweetness of the vanilla balances the beer's deep malt, and those subtle chocolate notes make for a chocolate-vanilla swirl in your glass.
Most importantly, it's still beer even after the ice cream has melted.