This shopping mall is right next to the Montparnasse Tower so finding it is not a problem. (The Tour Montparnasse is the tallest building in Paris and is on the Left Bank). The shops inside are the standard mall shops like 1-2-3 and Habitat and such. But this mall does have its very own Galeries Lafayette which makes it a standout and also its own C&A which is a German-based department store (think JC Penny's). For eating and theater options, those are mostly to be found all around the mall. This part of Montparnasse is a commercial district so anything you don't find in the mall you'll find across the street and also along rue de Rennes. This is a good option for when going outside the city is too much of a time commitment but you still have that shopping list to get through.