A marketplace was a large central gathering place where merchants sold their goods.
The Promenade aboard Deep Space 9 featured several shops. (DS9: "Emissary", "Meridian" et al.)
The city on the planet controlled by the Mokra Order had a marketplace where fruits, bread, and technological equipment was sold. The walls were decorated with posters and neon signs. (VOY: "Resistance")
A marketplace was also a central gathering point for vendors and visitors on the Mari homeworld. The marketplace was also the place where Frane attacked Terril and Tembit killed Talli. (VOY: "Random Thoughts")
The marketplace in both episodes was built on Paramount Stage 16.