"What a worthless creation that ghost was! I will banish it to the gap between dimensions!!"

The Gap Between Dimensions is a location mentioned in The Legend of Zelda: Ocarina of Time. After Link defeats Phantom Ganon in battle, Ganondorf banishes the phantom to the gap, calling him a "worthless creation".

It is unknown what exactly the Gap Between Dimensions is, but it can reasonably be anything from an empty void to the Twilight Realm.