The Basilique du Sacre-Cour was one of the highlights of our trip. Views from Montmarte are outstanding, and it is a very quaint area. The easiest way up is the funicular, which is included if you have a metro pass. Otherwise, it is a long hike up the stairs. I want to warn people about the "Jamaicans with the string." These guys stand around the outside of the stairs and funiculars to try to trap you into buying a bracelet made of string. They will ask you to hold the string for them, then quickly make a bracelet and tie it around your wrist. Then they will try to charge you 20€ for it. Don’t fall for it!
The Sacre-Cour has the most beautiful mosaics; unfortunately, they don’t allow you to take photos. The interior is really dark and has a very solemn feel to it, but it really makes the mosaics stand out that much more. I read that the crypt is supposed to house a piece of Christ’s heart, but I couldn’t find where it was supposed to be. The gift shop has a large assortment of rosaries, postcards, and other religious merchandise.
Once you’re done, walk around the area surrounding the Sacre-Cour. The shops are very touristy, but there was a great little art fair the Saturday we were there. Be aware, though, there are a lot of street peddlers that want to draw your picture, too, and they can get a little annoying. We took the stairs back down, and it had this really cool "Parisian park" feel to it. Another thing you may want to do while you are in the area is grab some sweets from the patisserie, Le Gostelier, across from where the funicular is, and sit and enjoy the park and carousel. We did a little sampler of mini pastries, and it was really yummy.