Elemental Sanctuary

The Elemental Sanctuary is a realm in between the Minish World and Hyrule. It contains a podium for infusing the Four Elements into the White Sword to create the Four Sword. It also contains a stained glass window which tells the story of the Light Force the Hero of Men and the Picori Blade.

The Elemental Sanctuary appears in The Minish Cap, and disappears by the end of the game. However, the altar where Vaati is sealed in Four Swords and Four Swords Adventures is more than likely the Elemental Sanctuary, and even contains the Four Elements on their pedestals.