The Sun Dial is the sixteenth and final puzzle in Virtual Villagers 3.
The Sun Dial room will only appear once you've solved the previous 3 puzzles (13, 14 and 15).
Drag a villager onto the Sun Dial and move the green circle to the position.
You will have to wait until rays of light hit the Sun Dial. At that point you'll see 2 ghosts bouncing over the mark on the Sun Dial.
Drag and drop a villager on the ghost picture and all your questions will be answered.