Where’s your nearest water source? How easy is it to protect?
Having enough room to grow vegetables is a moot point unless you have enough additional supplies to support you whilst you wait for the food to grow.
What’s the soil like? What can you grow there? What’s the climate like?
It takes about one acre of land to support one person, how many people are you supporting?
The walls might keep shambling hordes out, but what about raiders and the like? Will you have enough people to secure it? Will you be able to feed and water those people with the space you have?
And speaking of water sources, how good at not pooing in it are you?