The castle is the second area on the island, to the right of the Village.
On The Top Of The King And Queens Castle.
It is on tp of the castle roof in astro knight island
Once you have built a new spaceship on Astro Knights Island, it will park on top of the castle whenever you leave the island.
Walk to the right.
its on top of the castle
There is no jail on Astro Knights Island. There is a castle dungeon, where an attacking alien robot is being held after his capture. (see the related question)
On the top of the castle
There is a castle on Astro Knights Island, in the kingdom of Arturus.
it is to the right of the castle, just keep going right.
This means you have already completed the Arturus part of Astro Knights Island. Your spaceship should be parked on top of the castle if you return to the planet.
on the castle
The King and Queen of Arturus are on the second floor of the castle.