I think Nessum Dorma is the most often-ever performed single from the opera Turandot. Turandot has other great pieces in it, but tons of people just love Nessum Dorma.
In English the words are something like this:
None shall sleep! None shall sleep!
Not even you, oh Princess,
in your cold bedroom,
watching the stars
that tremble with love, and with hope!
But my secret is hidden within me;
no one will know my name!
No, no! On your mouth,
I will say it when the light shines!
And my kiss will dissolve
the silence that makes you mine!
[chorus of women is heard singing in the distance]
No one will know his name,
and we will have to, alas, die, die!
[Calaf, a certain of victory, sings:]
Vanish, o night!
Fade, you stars!
Fade, you stars!
At dawn, I will win!
I will win! I will win!