Ganon's Tower (A Link to the Past)

Ganon's Tower lies in the Dark World atop of the world's imitation of Death Mountain. The tower was sealed shut and protected by a glowing magical force. Only when Link had gathered the Seven Crystals did the tower reveal its entrance in the form of a staircase. Inside, Link battled Agahnim and drew out Ganon who transformed into a giant bat and escaped to the Pyramid of Power.