The Elemental Sanctuary is Bridged between the Light World and the Minish World. The entrance to the Elemental Sanctuary can only be seen by Hylian children and the Picori, but the entrance only reveals itself once every century.
Link will go to the Elemental Sanctuary after he acquires one of the Four Elements. When Link arrives here he places the Picori blade in the pedestal, this makes all the current elements Link has fuse into the Picori Blade making the White Sword. Also the more elements Link has fused into the sword the more clones he will be able to make. Once you get all the elements it will forge the Four Sword giving Link the ability to make four clones .