Throughout the surface below the clouds are solid grayish cubes. These cubes are special and known as Goddess Cubes. You cannot normally destroy them. Only the hero chosen by the goddess (Link) can activate them, and only through a Skyward Strike.
This causes the Cube to shoot up into the air, unlocking a specific treasure chest among the sky. Generally, they appear on your map (except for those in Skyloft and those Inside the Thunderhead (until you enter either, the latter for the first time)). These chests can contain very, VERY special rewards, among them Pieces of Heart and Gold Rupees.
Throughout your travels, you are also likely to find the dark-colored chests. These are also Goddess Cube chests, just those haven’t been triggered.
Anyhow, this section is made to list the Goddess Cubes organized by area. You will also receive detailed information on how to find them, the location of the chest, and what is within the chest.