Place mint leaves in a medium bowl. Bring water and sugar to boiling in a small saucepan, stirring until sugar dissolves. Remove from heat; pour over mint leaves. Stir in orange peel, orange juice, and lemon juice. Cover; let stand at room temperature for 1 hour. Strain. Cover and chill for 4 to 24 hours. Serve over ice. If desired, garnish with mint sprigs. Makes eight 4-ounce servings.