The Marais is my favorite neighborhood in Paris. It includes the 3rd and 4th arrondissements and offers 16th century architecture, Israeli street food and wonderful shopping. The Marais is also one of the rare parts of Paris that is lively on Sundays but know if you go that day you will encounter large crowds. I recommend visiting midweek when shops are open, but it’s a bit more quiet. Here is a video guide to the area.
Travelproper tip: The Marais is home to the Jewish Quarter of Paris and because of this many of the restaurants along Rue des Rosiers are closed on Saturday.