Grizelda's castle is the home to Grizelda and Frookie. It is a large castle made of pink crystals and is located atop a mountain in the Rainbow Kingdom, surrounded by hundreds of purple trees. It is also the indirect home of the Grizmos, as their home is directly below the castle, supported by a pillar of crystal used to construct the castle.
In "Great Grizmos!", Grizelda used so much of the Grizmos' pillar's crystals for renovations that the castle began to sink. With True and her Wish help, the sinking was stopped and everyone was safe.
In "Princess Grizbot", the castle was in danger of being destroyed by the giant robot, but was saved by True. In the same episode, Grizelda's bedroom was revealed.