The Sacred Realm
The Golden Land, as it is refered to as, is one of the more fantastical locations in the Zelda world. The Sacred Realm is a mythical plane created by three goddesses to be the holding place of the Triforce, an artifact of great power.
The triforce, is composed of three golden triangles, with each one representing the essence of the goddesses that created the world; Din's Power, Nayru's Wisdom, and Farore's Courage.
In Ocarina of Time, the Sacred Realm remained sealed away behind the Doors of Time until three spiritual stones were gathred and the Song of Time opened the doors. Each spiritual stone represented a race from Hyrule, and as well, one of the goddesses. The Kokiri Emerald represents Farore, the Goron's Ruby represents Din, and Zora's Saphire represents Nayru. The Temple of Time stood as the gateway to the Sacred Realm, inwhich also housed the Master Sword, which can only be weilded by the Hero of Time.
Link and Zelda learn of Ganondorf's plans to gain control of the triforce, and plan to enter the Sacred Realm first. As Link is too young to weild the Master Sword, his spirit is sealed away in the Temple of Time until he is old enough to become the Hero of Time, leaving the Sacred Realm open for Ganondorf.
However, all was not lost. Ganondorf's heart was not in balance, causing him to gain control only over the triforce of Power, with the other two to return to their holders, Link and Zelda. Ganondorf did however, gain control over the Sacred Realm causing chaos and turmoil.
Once Link defeats Ganondorf ( Ganon ), Zelda and the Sages seal Ganon away (said to be the evil Realm in OoT). Ganondorf vows to eliminate the descendants of the Sages.
The Sacred Realm is also refered to as, the Dark World. We see this in A Link to the Past. This name came from the Sages, as they refered to this corrupt world. In A Link to the Past, Ganon has Agahnim capture the seven descendants of the Wise Men to break the seal to the Golden World.