Final Fantasy VII Walkthrough
1.19: Mt. Nibel
Cloud finds out that Tifa is the guide, and there is a picture taken of all of you before you head up. Once you get control again, you can look at your menu, but nothing can really be changed. Cross the bridge, and head forward. You fight enemies, but having Sephiroth in your party makes things easier. Once you're off the bridge, head up and to the right.
Head all the way up, then out, and you'll see a natural mako fountain. Once you have control again, head inside of the mako reactor.
Head forward, then left along the pipeline, then jump to the boards, jump to the chains and climb down. Go to the right, into the entranceway. Talk to Sephiroth, fix the valve, then talk to him again to look through the window. You then have the option to save your game.