Across from the inn is the office of Louis Merse, Flotsam’s royal burgomaster. He pays Geralt for completing certain side quests and also controls the Royal Mail in Flotsam (which is relevant to yet another quest). You can also drag an astonishingly high quantity of loot out of his house and office.
Between the guard post and Merse’s office is one of the exits leading out of town. This particular one passes through a small walled area and another door to emerge in the village of Lobinden. There are two training dummies in this area that you can knock over with impunity (since the guards here are always asleep).