From which opera...

I only saw a small portion of this film, in which an aria is sung. I recognized it, but can't remember what it was, from which opera. Shame on me, yes.

It's the scene in which two women are looking down from a balcony and below on the street is a band, and a woman singing. That's a fragment of a hauntingly beautiful aria. But which?

Clarifying this mystery would be greatly appreciated. Thank you.