Many people get lost once they get to Jadd because they cannot find the entrance to Medusa’s cave. A boy in the town of Jadd will tell you something like “Palms trees and 8” after you give him some enemy fangs, but this doesn’t help much.
So here is what you do. From the entrance to Jadd go South, East, South, South, East, South, South, West, North and you will find yourself at this screen.
On this screen, without riding your Chocobo, walk figure eights around the two palm trees, try both directions if it doesn’t work. The cave will open up for you after that, and you can continue your adventure!