By DrewAlthough Carmen is Bizet's best-known opera, his best-known opera aria - indeed, one of the most famous in all opera - might be "Au fond du Temple Saint," from the seldom-performed Les pêcheurs de perles (The Pearl Fishers).
I recall that during a Met Opera quiz a couple of years ago, one of the panelists suggested The Pearl Fishers was due for a revival in the operatic repertory. Indeed, Nathan Gunn starred in a wonderful production of it last year at the Lyric in Chicago, and it opens the Minnesota Opera's season this fall. However, although the opera iteslf isn't regularly seen, "Au fond du Temple Saint" is a staple of concert performances.
I'm not quite sure why The Pearl Fishers isn't performed more often, but after having heard it one possibility comes to mind: it requires really, really good singers. The most famous recording of "Au fond du Temple Saint" features two all-time greats, Jussi Björling and Robert Merrill; unfortunately, there's no video of it, which can be a problem if you're planning to do a video post. (Seldom-performed operas seldom have videos, unfortunately.) Nevertheless, if you want to hear it (and you really should), you can listen to it here.
For those of you in a more visual mood, here is a concert performance by Roberto Alagna and Bryn Terfel. After listening to it, I think you'll understand why "Au fond du Temple Saint" is considered one of the greatest arias of all time.