Place des Voges, the royal court of the 16th century is also in the Marais. Now home to a couple of homeless folks, and a public park for everyone. That is where Victor Hugo's house is too! Not to mention the site of the old Bastille is just down the road.
Las du Fallafel is in the Jewish part of the Marais. Some of the best food in the city! And don't forget Pain de Sucre that has lovely macaroons and homemade marshmallows!
The WWII Jewish memorial is the in Marais along with the Picasso Museum and the Center Pompidou, the National Archives, and a scatter of other little museums. There is something to do every moment!