You’ll be on the other side of the crumbling wall of the Temple of Time. You’ll be watching a fairly lengthy scene, one I will not really spoil for you. I’ll just, for the moment at least, let you know that Zelda hands over the Goddess Harp.
After the scene, you are to go to the old woman at the Sealed Grounds. (If you forgot, like I did, this is in Faron Woods.) While here, you can blow away the sand for some goodies and use the Beetle to get some Rupees from the pillars nearby.
Afterwards, go across the bridge and speak with Gorko. Then use the Bird Statue and return to the sky.