Ganondorf then revives, and Midna teleports Link and Zelda outside the castle so she can hold him off with the Fused Shadows. However, as Hyrule Castle collapses, it is revealed that Ganondorf was victorious as he crushes Midna's helmet. Ganondorf engages Link on horseback, and, assisted by Zelda and the Light Spirits, Link eventually knocks Ganondorf off his horse and they duel on foot before Link strikes down Ganondorf and plunges the Master Sword into his chest. With Ganondorf dead, the Light Spirits not only bring Midna back to life, but restore her to her true form. After bidding farewell to Link and Zelda, Midna returns home before destroying the Mirror of Twilight with a tear to maintain balance between Hyrule and the Twilight Realm. Near the end, as Hyrule Castle is rebuilt, Link is shown leaving Ordon Village heading to parts unknown.
What does Midna destroy?
Mirror of Twilight