Inside Hyrule Castle is the fourth dungeon in The Legend of Zelda: A Link Between Worlds. As its name suggests, it is the interior of Hyrule Castle. Although most other dungeons in the game may be completed in any order Link chooses, Inside Hyrule Castle must be attempted after immediately after clearing the Tower of Hera and the House of Gales as well as retrieving the Master Sword.
After acquiring the three Pendants of Virtue and retrieving the Master Sword from the Lost Woods, Link is able to break the magic barrier that Yuga placed around the castle and may enter its interior, intent on rescuing Princess Zelda. He is too late to save her, however, and witnesses Yuga transforming her into a Portrait halfway up the castle. Yuga is surprised to see that Link emerged, but does not let this faze him and continues to the Fissure at the top of the castle. Link continues to fight his way to the top floor of the castle to try to defeat Yuga. At one point they fight but Yuga retreats to Lorule Castle and begins the ritual to revive Ganon before allowing Link to defeat him.
Like the Hyrule Castle Tower in The Legend of Zelda: A Link to the Past, this dungeon is fairly linear and does not use puzzles to hinder Link's progress. Instead, the castle is filled with a large number of enemies, giving Link a chance to become accustomed to his newly-acquired Master Sword.