My bad, should've been specific. The forts are what I mean, and hopefully not to difficult to make..
A:http://news.sketchucation.com/files/2009/06/roman_fort.jpg
B:http://library.thinkquest.org/22866/Dutch/Plaatjes/fortnl.gif
Really, not many variations of the forts in question, you could use the visual of the one shown in the movie
'The Eagle'. It had moat with spikes instead of water with an earthen wall that went up with a wooden palisade with the buildings within. Sorry, couldn't find any pictures of the actual one.
Haven't been to Hadrian's wall yet, but do you have any plans on making the wall a castle/fort/settlement of some sort?