Skull Dungeon

In A Link to the Past
The Skull Woods Palace is the third dungeon in the Dark World in A Link to the Past.

It is located in the north-west, in the area also known as the Skull Woods. The main treasure is the Fire Rod, and the end boss is Mothula. After defeating him you receive a Heart Container and the 3rd Crystal.

This dungeon is interesting because instead of a single main entrance, the Lost Woods contain multiple entrances to the dungeon. Entrance is gained by various holes and pitfalls throughout, and the final entrance to the boss is gained by a huge, ugly skull head where the Master Sword used to be. This makes it unique among the dungeons so far featured in the Zelda series.

In Oracles of Ages
The Skull Dungeon is Level 4 within Oracle of Ages. It is located in the present day Symmetry Village, but can only be accessed when you fix the Village in the past. In order to do that, you need to set the Tuni Nut in the middle of town. Once that is done, the village is fixed in the present and the dungeon is opened.

The main item within the dungeon is the Switch Hook, an item that allows Link to switch places with certain items and enemies. The mini-boss is the Armos Warrior, and the main boss is Eyesoar. The item you need to collect from the dungeon is the Essence of Time, the Burning Flame