Messina is a bustling port city, but its climate makes it agricultural as well, meaning the men returning from battle with Don Pedro would likely view Messina as a welcome respite from the battlefield. The whole point of the soldiers coming to Messina is that they’re in an idyllic setting, away from the action of the war.
While most of the play occurs around Leonato’s house, Leonato’s orchard (or garden) figures as a central place of action as well. It’s where Benedick and Beatrice hear the conversations about each other's "love." Language about the beautiful garden gives us a good feeling for the whimsical romance that characterizes the play.
The setting is also bigger than its physical realm – we learn that Messina is a respite from the battlefield because it sets the scene for the play to take place in a holiday-like mood. While the play is not a true pastoral play in the sense that everyone is unfamiliar with Messina, the soldiers’ presence in Messina shakes things up – the space is suddenly set up for matchmaking and merriment. The soldiers are in a loving mood now that their minds have turned from war, and Leonato’s house is excited to have the soldiers visit. The mood, like the atmosphere, is generally festive.