Sometimes called New Royal City, Dusit Park, Dusit Garden, or simply Dusit, is a complex of palaces and royal residences in the south of the Dusit district. The palace was established by King Rama V, the first Thai monarch to visit Europe. He was impressed by the royal parks and residences he had seen there, which were leafy, relaxed, spacious and cool, as opposed to the Grand Palace, which was cramped with buildings for his numerous wives, children, and servants. These buildings blocked air flow inside the Grand Palace, which heated it up considerably. As a replacement, King Rama V started building the Dusit Palace.
The main structure is the Vimanmek Mansion, touted as the world's largest golden teakwood residence and the former home of King Rama V. Get a ticket for 100 baht on the northwest side of the palace grounds, or enter for free if you still have the Grand Palace entry ticket (remains valid for a week). You can visit all the museums on the palace grounds with one ticket, except the Anantasamakhom Throne Hall and the Royal Elephant National Museum which cost an additional 50 baht. Keep in mind that the same dress codes apply here as in the Grand Palace, so leave shorts and sleeveless shirts in your hotel room. You must store your belongings in a locker before entering each museum. It's free everywhere, except at the Vimanmek Mansion, so if you're on a stringent budget, go to another museum first and leave your belongings there. The last (compulsory) tour of the Vimanmek Mansion starts around 15:15. Some of the smaller museums close at 15:30. Allow a full morning and afternoon if you want to see all the buildings and museums. Also make sure you get a map when buying the ticket, as the palace grounds are large and hard to navigate without a map.