In a medium saucepan over medium heat, combine blueberries, sugar, and water. Stir gently and bring to a simmer. Cook for about 5 to 7 minutes until blueberries burst and sugar dissolves completely, creating a vibrant syrup.

Remove from heat and allow to cool slightly. Strain the blueberry mixture through a fine-mesh strainer, using a spoon to press down and extract all juice. Discard solids and let syrup cool to room temperature.

Juice enough lemons to obtain about 1 cup of freshly squeezed lemon juice and strain to remove seeds and pulp.

In a large pitcher, mix cooled blueberry syrup with freshly squeezed lemon juice and 4 cups cold water. Stir well to combine flavors. Adjust sweetness or tartness as desired.

Refrigerate the lemonade for at least 1 hour to chill and meld flavors.

Serve the blueberry lemonade over ice and garnish with lemon slices and extra blueberries. Add sparkling water if desired.