I've been working on this thing off and on for probably three years...mostly off. I took the advice of a crafter on YouTube to build it out of cardboard. I won't be doing that again. While very inexpensive, it was very time consuming and boring. I used a dollar store Christmas gift box as the base as it were. The battlement was made by gluing the lid to the main part of the box and then cutting out chunks to make the merlons and the crenels. The part that took forever was cutting out and gluing the stones to the sides of the walls. I used pulp paper egg cartons. They have a nice bumpy texture. I ran out of egg cartons and used regular cardboard for the outside and inside of the battlement wall. I should have made the floor of the battlement out of stone, but for some reason, I made it to look like wood planks. I used strips of card board.
I sealed it all with a mixture of Mod Podge and black craft paint and then kept dry brushing it with lighter and lighter grays. For the wood, I painted it with a honey brown craft paint and then used made a wash of Future floor wax and burnt umber paint.
I think it turned out OK. The stones are not to scale, but I don't really care. It isn't meant for diorama purposes.
Recently, I bought a sheet of pink insulation foam. I plan to use that for my next terrain project.