Eyeglass Island Library

In Oracle of Ages, Eyeglass Island Library sits on a small island of its own on Zora Sea. It appears in both the past and present, the back room changing for each time period.

Present
The Library is initially closed off, both key and keyhole having disappeared. Eventually, Link discovers that King Zora holds the key. Until then, there is no way to enter unless he travels to the past.

After unlocking the library, the back room is revealed to be very different from the past, housing an old man and the final Book of Seals, the Fairy Powder having vanished a long time ago. By obtaining the Book of Seals, Link was able to use it to solve the puzzle in the past.

Past
The library is initially locked on the outside. A key is required to unlock the door. The back houses a puzzle that requires an ancient book from the present to complete it. Once completed, the old man situated in the middle of the room will give Link the Fairy Powder he guards.