Start with 1 bunch fresh basil, reserving a handful plus 8 small sprigs for garnish. In a medium saucepan, bring water, sugar, and remaining basil to a boil. Reduce heat, and simmer, stirring until sugar dissolves (about 5 minutes). Cool slightly, then refrigerate until cold. Strain into a pitcher, pressing down on basil to extract any liquids; discard basil. In pitcher, combine basil syrup, vodka, and lemon juice. Stir in reserved handful of basil leaves, sliced lemon, and sliced orange. Serve in tall glasses over ice; top with basil sprig.