Mirror Shard

This one of the four pieces to the Mirror of Twilight that Zant has broken so you couldn't reach him so easily. One piece you get is located in the Mirror Chamber where first learn of this, one is "in the moutains" which is where Snowpeak Ruins is, another is in a "hidden palace" which is the Temple of Time in the Sacred Grove, and the last shard is "in the heavens" which is the City in the Sky. Retrieve all these shards and head back to the Mirror Chamber, now that the mirror is fixed you can now enter into the "Twilight Zone".=)