The next sight along my way from the Marais neighborhood, walking along the Right Bank toward the Pont d'Austerlitz and the train station, was what I would call a yacht basin. It's called Le Bassin and/or Le Port de l'Arsenal. Until recent times, it was the site of a commercial port facility serving the city of Paris.
In the 1980s, the Port de l'Arsenal was transformed into what is called a port de plaisance. Boats in this harbor have access to the Seine through a narrow channel and a lock — the water level in the basin is three meters (nearly 10 feet) higher than the level of the Seine.
To the north is the Bastille, with its tall green column, and the Canal Saint-Martin leading up to La Villette and the north suburbs of Paris.When the old Bastille château-fort still existed — it was knocked down during the French Revolution after serving for hundreds of years as a much-hated prison — the ditch that had fed water from the Seine into its moat was dug out to create today's Port and Bassin de l'Arsenal.
In the 19th and 20th centuries the new basin became an important commercial port and carried mostly péniches — barges.
There are berths for more than 175 boats in the Bassin de l'Arsenal. The péniches you see in the port are surely barges that have been converted into pleasure boats or even house boats. At least one of the two above was for sale when I was in Paris (four weeks ago today!).