If you loved Solaris, try Nostalgia
A bridge between a film you've already seen and one most people haven't. Nostalgia has roughly 3.0× fewer votes than Solaris — it's a deeper cut, not a mainstream recommendation. Here's what they share, and what the second one does that the first one doesn't.
What they share
Both films are directed by Andrei Tarkovsky, and they both carry the cerebral, foreign gem, slow burn mood tags, and they sit in Drama territory. If that's the register that drew you to Solaris, the second film will land in a comparable space — through a different lens.
What Nostalgia is
Tarkovsky being Tarkovsky, here's another chance to ponder heavy stuff. A Russian poet in Italy, homesick, researches a composer and meets a local weirdo. It's the sort of film that can make you feel like you've aged a decade in two hours.

