|The Moon Castle in the anime|
The Moon Castle (ムーン・キャッスル) was the palace of the Silver Millennium Kingdom during the distant past on the Moon of Earth. It was the home of Queen Serenity and Princess Serenity, as well as many other subjects. There were also four guardians of the Kingdom and the Princess residing at the palace - Sailor Mercury, Sailor Mars, Sailor Jupiter, and Sailor Venus - as well as two feline advisors, Luna and Artemis. It was guarded from outside intruders by three other Senshi, Sailor Uranus, Sailor Neptune, and Sailor Pluto, though those Senshi were not known of by the vast majority of those of the Moon Kingdom.
There were also forbidden passages deep within the castle which led to the Space-Time Door. It was revealed in the manga that at the center of the Moon Castle was the Chamber of Prayer which housed the Crystal Tower.
In the live-action series, the Moon Castle was protected by a translucent dome of matter or energy surrounding it. In the Special Act, Queen Serenity sent the Legendary Sword from the palace down to Earth.