Duelist Kingdom (island)
During the Pacific War, the island was occupied by the U.S. military. Troops that died were buried in the caves under the island.
Maximillion Pegasus later came into ownership of the island and used as his own private residence. He sometimes invited others over to discuss business deals. Seto Kaiba visited the island to celebrate the completion of the holographic Duel Monsters technology, and Duke Devlin went to demonstrate Dungeon Dice Monsters to Pegasus.
Pegasus used the island to host the Duelist Kingdom tournament. For the tournament, he had various Dueling Arenas (Battle Boxes in the manga) set up across the island. During the tournament, Kaiba made his way to the island to take Mokuba back. Pegasus forced Kaiba to Duel both Yugi and him for the chance to save Mokuba. After Pegasus lost to Yugi at the end of the tournament, Yami Bakura attacked him and stole his Millennium Eye. In the manga, this killed Pegasus.
Pegasus Castle was situated on the top of a hill. In the anime, it was given a much longer staircase to the top. The Duelist Kingdom tournament finals took place here. To gain entry, a duelist must insert 10 Star Chips into a lock. This rule also applied to visitors wishing to see Pegasus during the tournament, including Seto Kaiba.
Inside the caverns were two main passages; one led to the graveyard, and the other led to the labyrinth. In the anime, the tunnels were lined with traps, such as a fake giant boulder, which rolled through the tunnels after someone stepped on a trap.
Joey was forced to Duel against Bonz in the graveyard. After he won, Keith had Bonz, Sid and Zygor trap Joey and his friends inside by pushing a large boulder in front of the entrance. To escape, they had to make their way to the labyrinth. Bakura was able to navigate through the tunnels in the direction of Pegasus castle, since his Millennium Ring was pointing at Pegasus' Millennium Eye.
The graveyard, called the crypt in the manga, was where Joey was forced to Duel Bonz. The area was lined with skulls and gravestones. In the manga it had a Battle Box, while in the anime it had a Dueling Arena. Zombie-Type monsters were given a Field Power Bonus here.
Bonz was given an advantage, since he made a Zombie Deck beforehand, but Joey managed to beat him.
The edges of the tunnel become smoother and straighten out into solid walls as the tunnels become the labyrinth maze.
Past the maze is another dueling arena, where the Eliminators, the Paradox Brothers, waited. This arena was set up for Labyrinth Duels. Past them was the exit to surface just outside the castle. In order to leave, entrants must defeat the Paradox Brothers in a Duel and choose from one of two doors, only one of which they said led out. In reality, both doors went to the same place, and the brothers tried to trick the players into thinking whichever door they picked was the wrong one.