St. Louis is the smaller of the two islands on the Seine River in Paris, located upstream of Sidai Island. It was an uninhabited island in the early 17th century. By 1664, the island had been filled with ventilated new houses facing the wharf and the Seine. There are many top art galleries and fashion stores on St. Louis. Sidai Island is famous for Notre Dame in Paris and has a lot of tourists. St. Louis Island is much quieter.