This is the Imperial Defense Line / Fortress Walls that I have been speaking of. This set of terrain will be used for an upcoming massive Apocalypse game that is now about 3 weeks away. Each section was made by using a wood "core" to support the foamcore, for extra stability (since after all, models are going to be placed on these things, so they might as well be sturdy). All the sections are modular, allowing them to be arranged in any manner. These are still a work in progress and more detail will be added before I go over the pieces with plaster.
Here you can see the size of the main gate section when compared to a Warwalker (60mm base), Crisis Battlesuit (40mm base), and a Fire Warrior (25mm Base). On either side of the gate section are two tower sections, each of those are a seperate piece that can be removed and placed anywhere to make up the walls.
Since the Gate is mounted with hinges, the entire gate is free to swing open/closed. The opening created is 16" wide. Easily large enough to accomodate tanks and other large models.
Here you can see all of the wall sections done up so far. Each is 12" long, and has room for 40mm and 25mm bases on the top of the wall.