In 1247, Saint Louis, (Louis IX) authorised construction of a new city opposite the medieval fortress village on the left bank of the Aude river. Marked by a series of square blocks that surround the Place Carnot, Carcassonne’s primary civic gathering place, the Bastide serves as the commercial center for the city. Restaurants, bars, shops, bakeries, a department store, grocery stores and civic, religious, and educational buildings as well as grand private residences and apartments are all found in the Bastide. There are two large art museums, one for contemporary art and one focused on classical forms (Musee des Beaux Arts). Easy access to the train station and bus connections and the Canal du Midi, as well as walkable distance to the mediaeval walled city make the Bastide an excellent choice for visitors to Carcassonne.
You can learn more by clicking on this link
https://www.tourisme-carcassonne.fr/decouvrir/la-bastide-saint-louis