Greatest Spanish movies of all time?

So I'm half English, half Spanish and have recently realised how little Spanish cinema I have actually seen. What are you guys' recommendations for titles that I need to check out? I've seen a few Almodovar pictures (which I love) and that's probably about it.

If you could limit it to Spanish productions rather than overall Spanish language (South America etc.), that would be much appreciated for this particular list that I'm going to make for myself!

Gracias!