Looks similar to Fallout 3 ruins.
I can't help but notice how much can be accomplished with sufficient concrete and forms to hold it. With a little forethought it is possible to make a site nearly impenetrable.
I like the "Walled City" concept. I have seen examples of this with sea containers. You have an interior area which is open to sunlight and weather but the outside is very discouraging and you usually have one point of entry which is a narrow choke channel. If you cover the interior area with silk tarpaulins or netting then it is difficult to even throw something over the wall into the courtyard.