Pedestal of the Master Sword

The Pedestal of Time (OoT) rests in the centre of a hidden chamber, in the Temple of Time. This chamber is blocked by the Door of Time.

The Pedestal of Time is the resting place of the legendary Master Sword. Link can draw the Master Sword from the Pedestal of Time, however, since he is too young to become the Hero of Time, his soul will be frozen in time for seven years, while his body matures and Ganondorf takes over Hyrule...

As an adult, Link can return the Master Sword to the Pedestal of Time, in order to travel back, seven years, and become a child again.