Ancient Castle of Ikana

In The Legend of Zelda: Majora's Mask, the Ancient Castle of Ikana is located deep in Ikana Canyon, and is home to the king of the long dead Ikana kingdom, Igos du Ikana. The Castle is the center of the once-great kingdom of Ikana. When the Garo Ninjas moved in nearby, however, the Garos infiltrated the fort and brought the kingdom to its knees.

The castle is an ancient building that is home to countless undead enemies, especially ReDeads and Wallmasters. You don't get an upgrade for clearing it, but you get the song Elegy of Emptiness. Once you finish the castle you will encounter Igos du Ikana, the ancient king of Ikana, and two of his minions. After using the Mirror Shield (which you got on the Bottom of the Well) to deflect sunlight to Ikana and his dark minions, and beat them, Ikana teaches Link the Elegy of Emptiness to help him reach and complete the Stone Tower.

The main entrance of this castle was sealed for a long time and will never open up again. Therefore you need to find an entrance somewhere else, the two accessible entrances are:
 * 1) Travel through the dungeon Beneath the Well to get the Mirror Shield, and you can enter the castle via a small well that is connected to backyard of the castle.
 * 2) The other entrance can only be used once you have the Mirror Shield or Light Arrows. It is next to the main gate and can be opened by removing the Sun block, by either reflecting a sun’s ray on it or shooting it with a Light Arrow.

Once inside you will have to get to the balcony outside and place a Powder Keg on the crumbled section to shine light into the castle (during daytime of course). Using this ray of light, you can remove the last Sun Block in order to get to Throne Room where the king and his nameless servants are waiting for you. After defeating them you will learn the Elegy of Emptiness.

The ReDeads inside the ruins react to the Gibdo Mask, Garo's Mask, Kamaro's Mask or the Captain's Hat. They start dancing as soon as Link dons one of these masks. This is so because they were once members of the Castle's dancing troupe before they died.