Ancient Tomb

The eighth dungeon in The Legend of Zelda: Oracle of Ages, the Ancient Tomb is located within the Sea of No Return. The "Sea" is actually dried up, revealing a great maze filled with strong adversaries (Darknuts and Lynels). Within the stone halls of the tomb are many twists, turns, traps, and treasures. The main treasure that Link obtains within these ancient catacombs is the Power Glove. Link must then use this new found power to take on the tomb's boss: Ramrock. After defeating Ramrock, Link is rewarded with the Falling Star (the last Essence of Time).

Background
The history, and the disappearance of, the Ancient Tomb is a great mystery. With its loyal guard, the Sea of No Return, few to no one could ever reach the tomb alive. Those few who did were quickly dealt with by the Darknuts and the Lynel who waited to meet them. A secret entrance on Crescent Island was created, in the shape of what the Tokay call their guardian, a stone head. It is currently unconfirmed if the head was created exactly for this purpose, or simply used for it.

Exactly who the Ancient Tomb is tomb to is also never revealed. It is possible the Ancient Tomb was for many, rather than just one person, given its size.

At some point, during the four hundred years which Link traverses while traveling in time, a bizarre change occurred: The Ancient Tomb vanished, the Sea of No Return vanished, and the key to the Ancient Tomb's access, the stone guardian, became the dungeon called Moonlit Grotto.

Perhaps not by accident, the former site of the Ancient Tomb would later become a graveyard. Yoll Graveyard, to be precise.

Quite likely, the mystery of how this tomb simply vanished from history, along with its guardian sea and secret passage, will never be solved, outside of theory.