We really have no intentions of seeing the Sacre Coeur when we got to Paris, but our hotel staff recommended it, so we headed that way. This church was definitely worth the extra time on the metro. We didn't have any wait to get inside, as we got there pretty late in the day. As soon as we walked in, we noticed the great paintings on the ceiling over the alter. There were also so many detailed carvings to look at. People were more respectful here than they were at the Notre Dame. There is also the option of climbing the tower, but honestly, the view from up on that hill is good enough without putting further strain on my knees.
I will say that despite the beauty of the church, the area outside does not appear to be the safest. There were pickpockets at work and we saw people using drugs. There were also a lot of people drinking on the steps out front.