1/2 C. sugar
4 1/2 C. cold filtered water
1 C. fresh lime juice, plus 24 very thin lime slices
1 pint fresh blackberries

Bring sugar and ½ C. water to a boil in a saucepan. Stir until sugar dissolves completely. Let cool to room temperature. Stir together lime juice, sugar syrup, and remaining 4 C. water in a pitcher. Serve in tall glasses over ice and garnish with lime slices and berries.