Near the end of the The Dark Knight Rises,
Batman is about to fly off with the bomb to save Gotham City. Commissioner Gordon wishes to know who Batman is, so the city can know who this masked hero is. Batman mentions that the mask is a symbol, that anyone can be etc.
He doesn't directly reveal that he's Bruce Wayne, but he says something before leaving. As Batman lifts off, the scene flashes to Gordon taking care of a young Bruce Wayne after his parents were killed. Gordon figures out that Batman is Bruce Wayne.
What did Batman say? And from that, how did Gordon figure it out?
The audio for Bane and Batman in this movie is a difficult to understand-- I kind of wish there were subtitles.