Level 1

Eagle Labyrinth, or simply Level 1, is the first dungeon in The Legend of Zelda and, by extension, is the very first dungeon seen in the entire Zelda franchise.

Entrance to the Labyrinth
In both quests, the Eagle Labyrinth is found on an island which Link reaches by way of a bridge. The island is in the center of a lake, and no previous items are needed to go there. The entrance itself is inside one of the brown trees.

First Quest
The interior of this dungeon appears to be made of stone bricks, like most dungeons in The Legend of Zelda, with its primary color being teal. Since it is the first dungeon in The Legend of Zelda, it is often considered as being one of the easier and shorter dungeons in the game.

The main items of this dungeon in first quest are the Boomerang, guarded by a room full of Goriya, and a Bow, although it will not come equipped with arrows, forcing Link to purchase some from one of the shops in the Hyrule overworld. The boss of the dungeon is Aquamentus, who guards one of the Triforce pieces.

When viewed on a map, this dungeon appears to be in the shape of a bird, with the tip of its right wing being the room containing the dungeon's Triforce piece. The dungeon's name is an obvious reference to its shape.

Second Quest
The Eagle Labyrinth's entrance is in the same location as the one from the First Quest. The dungeon's layout, however, like that of most dungeons in the second quest of The Legend of Zelda, greatly differs in size and difficulty. The dungeon's walls and flooring are again teal in color.

The main item of this dungeon is reduced to only the Boomerang which is again guarded by a room of Goriya, and the Bow have been moved to another dungeon location. Aquamentus also returns as this dungeon's boss, guarding one of the Triforce pieces as before.

The most notable difference in the shape of this dungeon is that it is changed from the shape of an eagle into the shape of the letter E, sharing a common link with most second quest dungeon that use letters to make up a word. When the shapes of the Lizard Labyrinth (Letter Z), Eagle Labyrinth (Letter E), Manji Labyrinth (Letter L), Snake Labyrinth (Letter D), and Moon Labyrinth (Letter A) are listed in that order, they spell Zelda.

First Quest

 * Blue Keese
 * Stalfos
 * Gel
 * Red Goriya
 * Blade Trap
 * Wallmaster

Second Quest

 * Red Goriya
 * Blue Keese
 * Stalfos
 * Blue Goriya
 * Blade Trap
 * Gel
 * Moldorm
 * Blue Bubble
 * Wallmaster

The Legend of Zelda comic
In the Legend of Zelda comic, Princess Zelda enters the Eagle Labyrinth to practice fighting in Ganon's Underworld. Link reminds her that if she needs help at one point, she can just blow the Magic Whistle and he will be there to assist her. The princess heads in, confident in that nothing could go wrong with all of the lessons Link has taught her. After Zelda vanishes into the Underworld, a Wizzrobe  commands several of Ganon's minions to tie Link up so that he can   teleport both of them into the final room of the labyrinth, revealing  to  Link that he filled the Eagle Labyrinth with the most dangerous of   enemies so that Zelda may not stand a chance up against them.

Meanwhile, just as Zelda is telling herself that she will not call for Link's help at the first sign of danger, a Gohma appears behind her. Surprised that a Gohma has appeared in such an early level, the princess tries to fire a Sword Beam at the foe's eye, but she is pushed back by the force of the beam, blaming Link for not having told her about the "kick." She is successful in defeating a group of incoming Patras,  although she admits to herself that the current situation is too tough   for her and decides to call Link by blowing the Magic Whistle. When Link does not appear, Zelda realizes that something must have  happened and tries to stay calm since she can still get out by   remembering everything that the young hero taught her. The princess then reaches for her magic pouch and gets out a bomb, recalling Link's advice in that she can find an exit by blowing up one of room's walls. The opening reveals even more of Ganon's minions, but still the princess manages to get into the next room since the foes are busy fighting amongst themselves. Zelda then prepares another bomb since she hears someone approaching her, which just turns out to be Miff.

Before Miff can say anything else, she warns Zelda about the Dodongo  behind her, allowing Zelda to defeat it with her last bomb. Miff realizes that the princess is hurt, and as the fairy heals her wounds, the princess explains to her the recent strange events. Astonished, Miff explains that Zelda cannot hope to fight through the  Underworld's labyrinths using Link's way since she considers that the   young hero only survives because of his "dumb luck and brute force." Zelda realizes this and wishes she had a bow with her since she is unable to fire a sword beam correctly.

Soon after, Miff and Zelda stumble into the treasure of the Eagle Labyrinth, a magic bow, which allows the princess to defeat the Gohma with a single shot and make her way into the final chamber of the maze. With her bow in hand, Zelda eventually defeats the Wizzrobe and rescues Link in the process.

Trivia

 * The Eagle Labyrinth and the Gnarled Root Dungeon from Oracle of Seasons have several similarities. The exterior of both dungeons is what appears to be a dead tree in a small island within a lake, and both dungeons have Aquamentus as the main boss.
 * In Norse mythology there is a dragon named Níðhöggr that gnarls on a root of Yggdrasil, compare with the fact that the boss of this dungeon is a dragon that lives in a tree based dungeon.