It is definitely worth a trip here to Montmartre, especially on a clear day. Take the Line 12 metro and get off at Abbesses, then take the long elevator ride up. The walk to Sacre Coeur (Paris's highest place) is only about 10 minutes from the Metro station. Many local boutiques, bakeries, shops and card shops on the way there. Once you get to the base of Sacre Couer, you have a choice to either climb the steps ~150-200 of them to get to the top or either take the funicular car up instead. If you have a Navigo Card or or Metro ticket, both are accepted.
The view from Sacre Coeur included the Pompidou Centre, Montparnasse Tower, the Pantheon and the skyscrapers all the way to La Defense. Make sure you go over to Place du Tetre, just follow left of Sacre Coeur , up the small narrow streets-- it is the place where all the aspiring artists assemble with their pieces of art work on sale and you may see them in person painting. You may also get a caricature done here also. Many local stores here selling all kinds of Parisien Souvenirs as well as many restaurants. Nice to come for an afternoon.