Chase away the winter blues with this bright, tart drink.
Bring water and sugar to a boil in a large saucepan, stirring until sugar dissolves. Add lemons and rosemary. Reduce heat, and simmer for 10 minutes. Remove from heat. Let stand for 20 minutes. Strain. Return to pan, and boil until reduced by half, about 5 minutes. Let cool completely. Fill each of 6 glasses with 3/4 cup sparkling water. Stir 1/4 cup syrup into each.