Goddess Cubes are objects from The Legend of Zelda: Skyward Sword. They are large blocks scattered across The Surface. When Link strikes one with a Skyward Strike, it will vanish, sending a ball of energy into The Sky. A corresponding Treasure Chest will then activate in the sky, turning from gray to a glowing purple and allowing Link to open it. When he receives the Goddess Whitesword, Link can unlock the ability to dowse for them.
Their name comes from Goron Archeologist Gorko, who gave them the name "Goddess Cubes" due to their association with the Goddess and their cube-shape. According to Gorko's research, the Goddess Cubes where placed on The Surface to aid the chosen Hero. Goddess Cubes are one of the primary ancient artifacts studied by Gorko, along with Goddess Walls. After obtaining the Goddess Whitesword, Fi will register them as dowsing targets if Link speaks to Gorko at Eldin Volcano near the Volcano Entry Bird Statue.
There are 27 Goddess Cubes in total, which correspond with the 27 Goddess Chests found in the Sky. Depending on their location, some may require Link to reach a certain point and/or obtain certain items to get to them and/or within range of his Skyward Strike. Like Goddess Crests, can be activated by any form of Skyward Strike (such as Skyward Strike enhanced thrust, Jump Attack, and Spin Attack) that hits them.
Goddess Cubes appear to be made of the same material as Goddess Crests, Goddess Chests, and Goddess Walls. As they where likely created by Hylia, they may be made of a divine substance/material that is sensitive to the energy produced by the Skyward Strike.