???? is a secret location in the game situated near the Hidden Village. It can only be accessed by 100%'ing the game - i.e. you must have the best weapon and armor (Space-Age Morningstar and Ancient Armor), all four tools (Slingshot, Bombs, Javelin, and Artifact), all the collectibles (Nebula Armlet, Blood Ring, etc.), all 23 Heart Rubies, and all 42 Moonstones.
As it's located near the Hidden Village, ???? is a forested area much like the village itself. It is a relatively small area with no enemies whatsoever and no objectives other than to reach the top of the level, after which you will receive the achievement Last Song of Earth. Upon entering the area, you will find yourself at the foot of a small mountain. To climb it, you'll have to use the Javelin to climb the stone walls and use the Artifact to reveal some invisible walls that can help you climb up further. At the top of the mountain, you'll find a stone wall that you must blow up with Bombs or a charged Javelin. Once that's done, you can enter the mountain and go into the next room, which features four strange capsules embedded into the cave wall. Once you approach the capsules, a song called The Last Song of Earth will play and you'll get the achievement of the same name. You can also go further to the right to go to the other side of the mountain, where you'll find a cliff with a beautiful sunset view in the background.
- Aside from Mul Cavern, this is the only location where the Fairies' Streaks occur spontaneously rather than being limited to the Zophiel Statues.
- The Last Song of Earth is the only song in the soundtrack that is unlisted.