Three-Eye Rock Palace

Located in southeast Hyrule, Three Eye Rock Palace is the sixth dungeon in Zelda II: The Adventure of Link, and is visited by Link during his quest to place one of the shards of the Magic Crystal to its lectern to find unseal the entrance of the dungeon right west of this one to find the third fragment of the Triforce and rouse Princess Zelda from her unnatural slumber.

Concept
Within the Palace walls, Link finds the Cross, useful to see invisible enemies, and defeats Barba, the incarnation of Volvagia after its decease in Death Mountain, in a past life. This palace is made of pink-colored bricks, and is notable for having fake floors (this is, hidden holes); it's also notable for being the only one with a mini-boss, Iron Knuckle boarding a vehicle, who is fought twice. The palace is hidden, it only appears if Link plays the Flute between the three peaks of Three Eye Rock. It requires Link to have the Magical Key, as no keys are here to open the locked doors within.