In a medium bowl, combine 2 cups of the cranberry juice, 2 cups of the pomegranate juice, ¼ cup of the lime juice and ¼ cup of the agave syrup; stir to combine. Pour mixture into a Bundt pan; top with half of the mint sprigs, and sprinkle with pomegranate arils. Freeze overnight.

Combine the remaining 4 cups cranberry juice, 2 cups pomegranate juice, ¼ cup lime juice and ¼ cup agave syrup in a punch bowl; add the gin and stir to combine. Just before serving, add the ice ring, lime slices and remaining mint to the punch; pour in the entire bottle of sparkling wine.

Kitchen Tip
To remove the punch ring from the pan, run the pan under warm water for a few seconds.