Fill a Collins glass one-third of the way with ice.
Add the pomegranate juice and rosemary simple syrup.
Fill the glass to the rim with club soda and stir gently.
Garnish with a rosemary sprig and serve. * Rosemary simple syrup: In a small saucepan, combine 1 cup brown sugar, 1 cup water, and 6 rosemary sprigs, and cook over medium heat, stirring frequently, until the sugar has dissolved. Let cool completely, then remove the rosemary sprigs. The syrup will keep refrigerated in a sealed container for up to three weeks.
