The line to get in was pretty reasonable. (In fact, we had little trouble with lines or weather our entire trip.) The inside is huge. It has countless naves and alters. The church is a Gothic structure, began in 1163 and still used as a Roman Catholic church. In fact, a mass began during our visit. We took entirely too many pictures to choose a reasonable amount, so instead, I offer some candles:
We climbed a narrow circular staircase to get upstairs, past the tall narrow windows that once allowed archers to protect it
and walked out to the second floor. It was a bright, colorful, open room with chairs on either side and a man who'd come out every now and again to shush us. I'm not sure if it's still in use for religious services, but they did have posters outside advertising a Vivaldi concert.
Next, we got back on the Metro and went to the Panthéon, originally a church and now a famous burial place for national heros.The inside is completely open with a few interred people and a LOT of statuary. There was also a pendulum in the middle of the room, busy marking off the time along with the rotation of the earth.