Feeling tired of the Middle Ages and want something Roman? This can be helped without leaving Paris, though there are just few remains dating back to the times of the Roman Empire. Pay attention to Arenes de Lutece which is a very small but attractive amphitheatre (especially if you remember you've found it in the middle of a big city), now reconstructed in parts. Roman baths are an option as well found near the Hotel de Cluny.
It may look you are in Rome, but it is really a parisian square: la place Paul Painlevé, in front of the Middle Age Museum.
This museum has a great collection of medieval are including several spectacular tapestires like the Lady and the Unicorn. This a small museum that can be visited in 2 to 3 hours.
Built on the site of an ancient Roman thermal bath, this museum is now home to the famed Unicorn tapestries. Open every day (with the exception of Tuesday) from 9:15 a.m. to 5:45 p.m.