This is one of three illustrations I have just started. Together I am working on an overall world map, this city map and a residential building.
Conceptually, Green Farrow is a halfling/hobbit town constructed in a motte and bailey style. The residents grow homes using espalier and topiary techniques to maximize the exterior space for cultivation. Defensive walls are grown continuously in ever widening bands to accommodate future growth. Underground tunnels connect the town and food cellars as well as give discrete passage beyond the outer walls. Lastly, it's design will attempt to add a natural obscurity to the casual viewer at ground level.
So, that's the inspiration, now the first couple of pics..
You can already see from the first sketch to the second that I expanded the city from a half round with a managed game preserve to a full 360. I agree these people are smart enough to enclose their Bailey all the way around...as was suggested to me by a clever friend.