Paris may not be known for its beaches, but it does have a thriving beach culture. Every year from mid-July to mid-August, the banks of the Seine River are transformed into inner-city beaches complete with deck chairs, grassy areas and palm trees.    The Left Bank beaches offer a more lively atmosphere with live music, games, and dancing. The Right Bank beaches are perfect for a relaxing afternoon, with pop-up bars offering glasses of your favorite cocktail.