Goron Mines

Goron Mines is the second dungeon or

Entrance to the Mines
Link enters the mines through a passage in Death Mountain, which he can access after defeating Gor Coron in a sumo match. His objective is to find one of the three Fused Shadows here.

Themes and Navigation
The inside of the mines is filled with lava and flame geysers; to avoid them, Link has to use his Iron Boots to stick to magnetized platforms. Some rooms are filled with water.

Link must seek out the three remaining Goron Elders, Gor Amoto, Gor Ebizo, and Gor Liggs, in order to piece together a key to get into the boss's lair. The dungeon has two floors and contains many large rooms, some with walkways over massive pools of lava. The mini-boss guarding the Hero's Bow is a Goron Guardian. The dungeon's main boss is the Goron Patriarch Darbus, who was transformed into the Twilit Igniter Fyrus.

Frequently-encountered enemies include Torch Slugs, Dodongo, and Beamos. Link will also encounter several Bulblins, which wield bows or clubs.

The Goron Mines also are notable for featuring what's possibly a Hylian advancement in terms of technology, mainly thanks to the complex machines that operate to keep the place functional, including magnetic cranes, elevators and minecarts; Link can take advantage of the machinery available to explore the dungeon. Link does not need to worry about the temperature, despite the hot environment.

There is a room with water at the bottom which contains multiple Bulblin archers that contains a Treasure Chest which can only be reached after retrieving the Clawshot from the Lakebed Temple. However, it contains a mere purple rupee. Similarly, within 's Fire Temple, there is a room which can only be reached by returning to the Fire Temple and using the Scarecrow's Song. The Longshot is required to obtain the treasure within.

Theory
It is possible that the Goron Mines are actually an expanded Dodongo's Cavern. Both locations are mines deep within Death Mountain that are very important to the Gorons, and both are also inhabited by Dodongo. As the years went by and veins of desired rock required ever greater effort to retrieve, the Gorons would have expanded Dodongo's Cavern and perhaps built structures to make mining easier, accounting for the rooms and machinery throughout the mines in Twilight Princess.

Trivia

 * This is the only dungeon in the game whose main treasure item is not obtained in the same room where the sub-boss is found. The Hero's Bow is collected one room after the battle arena where Dangoro fights Link.
 * Goron Mines is the only dungeon in the entire Legend of Zelda series in which neither the mini-boss or the boss (Dangoro and Fyrus, actually Darbus) are actually killed, both of them being good-natured Gorons and not actual enemies.