Opened in 1837, it's the city's second-oldest surviving Catholic church building (by some measures, anyway; this ranking is not as straightforward as it sounds). Check out these photos of the beautiful interior, taken on the final day of one man's two-and-a-half-year quest to attend mass at each of Manhattan's 96 Catholic churches.
That guy’s blog is bookmarked on my phone, very helpful in looking for churches and mass schedules, he has some nice pics of the churches, too.