Disney Castle

Though Disney Castle shows the palace and a little town on the World Map, the exploration is only limited within the castle, in almost all places that has been seen in the first game. King Mickey and Queen Minnie and other members of the royal organization hold meetings in the Audience Chamber. Hidden below Mickey's throne is another room called the Hall of the Cornerstone where the Cornerstone of Light is kept safe.
Below the castle is the Gummi Hangar, a room for storing and maintaining the Gummi Ship, and controlled by Chip and Dale. This room is accessed by entering a castle-like arrangement of foliage in the courtyard. Sora and his party later enter Disney Castle through this room when they visit in Kingdom Hearts II.
Other places to be explored include the Library, where Donald, Minnie, Daisy, and Goofy first read the letter from King Mickey about the danger of the universe. Minnie, Daisy and a broom servant can also be seen here anytime after you save the castle from Maleficent after returning from Timeless River. The Courtyard is the place where Donald catches Goofy napping, and where Queen Minnie and Daisy ask Donald to explain things in the beginning of Kingdom Hearts. The Colonnade in the castle connects the Courtyard to the rest of the castle. A town can also be seen on the world image of the castle on the world map. This town is where Horace Horsecollar and probably Clarabelle Cow, and Clara Cluck are living in after the Castle was built.
A pathway can also be seen when Donald rushes to tell Goofy about the King's disappearance in the first game. However, this pathway was deleted in Kingdom Hearts II.