Notice that the castle is on a hill or mountain (much as the later depiction in KQ8). Inspired by fantasy style castles.
Another depiction of the castle on a hill or mountain. Inspired by fantasy style castles.
Yet Another depiction of the castle on a hill or high point that slopes away from the castle. No moat is shown, and it appears the castle is based on the general look of the version in KQ5.
Castle Daventry as portrayed on cover of The King's Quest Companion, 3rd Edition.
Same as 3rd Edition but different color choices, and its clear that the castle is portrayed to be on top of a great cliff face (but of course the entire cover doesn't really reflect any strict portray of the world).