Sacred Realm

Overview
The Sacred Realm (聖地, lit. Sacred Land) is where the Triforce is kept. It is described as a golden land and is the home of the Temple of Light. The ancient Hyruleans prevented access to the Sacred Realm and the treasure held within it by sealing the gateway for all time. When Ganondorf gained entry to the Realm in Ocarina of Time, he seized the Triforce of Power and turned the Sacred Golden Realm into the Dark World, a twisted copy of Hyrule. The realm was restored to its once glorious state when Link defeated Ganon in an epic battle at the end of A Link to the Past.

A Link to the Past
The Dark World in A Link to the Past that Link explores during this adventure is actually called the Sacred Realm. The Essence of Triforce told him how Ganon had created the Dark World and told Link to touch the Triforce and wish for what he wanted.

The Dark World of A Link to the Past is said to be a corrupted version of the Sacred Realm. It is where most of the game takes place and where Ganon still hides, controlling things behind the scenes. The Essence of the Triforce informs Link that the Dark World will vanish upon Ganon's defeat.

Ocarina of Time
While the there is less action or gameplay in the Sacred Realm in Ocarina of Time, it plays a key role in the game. The Temple of Light, which houses the Triforce, is located at the very center of the Sacred Realm.

Each time Link completes a temple in the Adult portion of the game, a portal from the temple to the Temple of Light opens up. Upon entry into the Temple of Light, someone from Link's childhood awakens as a Sage, and bestows a medallion and some of their power upon Link.

After Ganondorf is defeated, he is sealed within the corrupted Sacred Realm by all of the awakened Sages.

The role of The Master Sword

In Ocarina of Time when child Link has collected all the Spiritual Stones and played the Song of Time - the door of Time opens. Behind the door of Time is big room where there is a pedestal with the master sword in. When Link draws the Master Sword he opens a path from Hyrule to the Sacred Realm and without knowing it letteing Ganondorf in. Link's body is then sealed away in the Sacred Realm for seven years until he is old enough to be the Hero of Time