Beneath the Well

In Majora's Mask, within Ikana Canyon is a seemingly empty well called the Gibdo Well; however the area Beneath the Well comprises a mini-dungeon which Link must traverse in order to gain the Mirror Shield and be granted entrance to the Ancient Castle of Ikana.

Entrance to the Well
The place is found right from the Spirit House, near where Tingle draws his maps. Although it can be entered anytime, full exploration of it is only possible after Link collects the Gibdo Mask.

Themes and Navigation
At the bottom of the well is a maze of colossal size, guarded by many traps and enemies. In front of each door within the maze is a Gibdo. In order to advance through the maze, Link must to speak to each Gibdo while wearing the Gibdo Mask and fulfill any need they might have. In each case, this will be a specific item which they will not request directly, but rather give Link a cryptic clue to decipher.

Enemies in the maze include Freezards, Dexihands, Black Boes, Keeses, Deku Babas and Wallmasters. A notable enemy within the well is a Big Poe; however, the only one there must be captured in a bottle and given to one of the Gibdos in order to proceed. At the very end of the maze lies the prize, the Mirror Shield, which grants access to Ikana Castle.

Beneath the well the Gidbos will demand Blue Potion, Five Magic Beans, ten Bombs, ten Deku Nuts, a Bug, Milk, A Fish, Spring Water, Hot Spring Water and a Big Poe. Most of these items will be found in the well, however, Link will need to get the Blue Potion and Magic Beans outside the well (both can be found in Southern Swamp, where the Potion can even be earned for free by trading two Magic Mushrooms to Kotake).

Trivia

 * The sign next to the entrance reads "Entry prohibited due to ghost sightings".
 * This is a unique area in the game because it contains the only regular Fairy Fountain. This requires giving many items to Gidbos and moving along a path that will fail to bring Link to the Mirror Shield.
 * It is heavily hinted that Pamela's Father became a Gibdo after he entered the well.