How to get out of the Northern Cave (spoilers)

As the crater is the best place for AP farming, a lot of players have been struggling to know if it's possible to get back to the Highwind. I've experienced the problem myself and not found enough valid information, so I'll just put the answer here.

Can you get out of the crater?

Yes, but there's a point with no return.

When we enter the crater and let Cloud do the "running" animation, we found ourselves in this place:

The black hole brings us back to the surface, where we can climb up the wall to reach the Highwind again: see picture to know where to climb.

About the AP farming: when the party meets up after splitting once, they talk about the final battle or something like that (sad moment etc etc). THAT'S when, if you continue, you can't walk all the way back. But until then you're always able to retrace the way and reach the Highwind.

Hope you found this helpful. Cheers!