In a medium sauce pan, combine 2 cups water and sugar and bring to a boil - stirring occasionally.Remove from stove and allow to cool down.Using a blender or food processor, puree 1 cup blackberries + 2 tbs lemon juice.In a large pitcher, combine water/sugar mixture and lemon juice.Using a fine mesh strainer, pour blackberry puree into strainer and stir contents into pitcher.Add additional 5 cups water and stir.Serve with ice and fresh lemons and berries if desired.