Put on the hover boots here so you don't get pulled down into the sinking sand. Up ahead is a crate, stand on it and use the longshot on another crate across the gap. From here, keep longshotting the flagpoles on the way to make your way further through the desert.
Eventually you reach a little building. First, go through the front door and down the ladder to a little area below. Use your fire arrows on the unlit torches to light them and make a chest appear containing 50 rupees. Be sure to kill the gold skulltula in here and get the token. Then go back outside.
Find the ramp going up to the top of the building and turn on the lens of truth to see a poe. It will start moving, so follow it. It's best if you don't lock onto it, just keep the lens of truth on and follow it as it goes along. If you stray too far from its path you get sent back to the beginning of the wasteland, and that's no fun. Eventually the poe will go a long way straight ahead to a solitary flagpole in the distance. When it starts to go back the way it came, DON'T follow it, just keep going straight ahead and you reach a new area.
Along the right wall of this expanse of desert is a cracked wall, bomb it and play Zelda's Lullaby for the ugly fairy to get Nayru's Love, a magic shield.
There's a dried-out pond a little bit further into this area. If you play the Song of Storms near it, it will fill with water and free some fairies that were trapped in the sand.
Now just go into the big temple up ahead.
There's actually nothing you can do in here except look at a small hole that you could crawl through if you were a kid (hint hint) and a gigantic block that's way too heavy for you to push, and read a couple of snake statues. Just leave.
Sheik will show up and teach you the Requiem of Spirit, allowing you to return to this temple no matter where you are... or what time period you're in. Now use the Prelude of Light to quickly get back to the Temple of Time. Return the Master Sword to the pedestal and you're back to the good old days of being a kid again.
Before we return to the Spirit Temple, let's tie up ALL the loose ends we left behind here in the past.