Prime Mart is the largest convenience store in the immediate area surrounding the Dulles Expo Center. It's big and well-stocked enough that it's likely to carry those last-minute groceries customers don't want make a grocery-store run for. It opens early and stays open until 9pm (most nights) and has a full selection of beers and wine, too. Services for lottery tickets, checks cashed and Western Union money orders are all available at Prime Mart.