This area is surrounded by baron rock, and has electrical storms and fierce winds everywhere. It is a twisty path that leads up to the side of the Northern Cave.
Soon after entering this section a sequence will play telling you of the arrival of the Shinra in the Highwind.
After this start to make your way up the paths. You will encounter more of the Black Hooded men, some of them will leave behind an item.
There are a couple of screens that are very hard to get across, as the wind knocks you down. Just watch very closely, and run across when the wind dies down.
Soon you will bump into Sephiroth, and after he is gone you can sit back and enjoy a bit more storytelling (including some of the best FMV sequences). When this is over you will find yourself back in Junon.
When you meet Sephiroth you have to fight Jenova-Death.