No idea whether this belongs in classic or not
La Luna - Bernardo Bertolucci
There's some really heavy themes in this, most notably and controversially incest between the mother, an opera singer (the whole movie is quite operatic in the setting of Rome) and her son, a teenager slowly being sucked into a world of drugs as he slips away from his mother. It doesn't cross the line all the way, instead hovers back and forth between a loss they've shared and a promise of being together at any means, albeit not in the conventional sense.
Lovely, epic music lacquers the scenery and intensity between the parent, who finds it a duty to be closer to the son thats torn between guilt and anger. Note though, that the physical incest is not as strong as the theme of emotional incest, which is usually the more pervasive of the two. It's main focus seems to be the mending of a mother-son relationship when both mother and son are wrecks to begin with.
Bertolucci has a fond place in my heart. As simple as this sounds, he makes films that are memorable and have something to tell us. Usually about politics and human sexuality. This film is one of his earlier works and its absolutely gorgeous. Speaking of gorgeous, Jill Clayburgh shows why she's so unsung, in this she plays a woman who's so respected to everyone but yet in shambles inside. I would love to see her in more and thank god I now have something to supplant her as Ally Mcbeal's mom.