There is nothing below the windmill, but Mordred's secret laboratory is under the hay bales to the left. To get the key :
(There are several answers at the related questions below)
You have to find the key. (see the related question below)
There is a written walkthrough at the related question below. There is a video walkthrough at the related link.
There are written solutions are the Related Questions below. There is a video walkthrough at the related link.
Astro Knights Island. (formerly Astroland :-) For e-mail updates from Poptropica, go to the related link below.
You have to replace the fuel rod and get some better coordinates. (see related questions below)
Nothing
The only place is in the castle dungeon, below the library. (see related question)
The dragon is mechanical, like all of Binary Bard's creations. (see the related image link below)
It is at X-11 Y-84 and looks nothing like the other asteroids. (see image links below)
The owl is in Mordred's hidden laboratory, underground below the hay bales near the mill. You will need a key to get in. (see the related question)
The solution to Astro Knights Island is at the related question below. Your quest is to rescue the Princess, who has been kidnapped by robot invaders and taken into space. Find and repair the saucer Excalibur and launch into space, to find the three planets where space knights are searching for the princess. Defeat the robot monsters on the planets using the Mystical Weapons of Arturus, then face the Binary Bard in his castle in another galaxy. (see related solution question)