There are no great Wars, but there are great War movies. The ones I grew up on always had a secret base or underground tunnel system. The hero had to find a way in and blow the whole mess up to save the allied forces.
The Underground War Room is much like that in that you can make it go on forever. Modular props can be lined up and linked to create whatever you need. At the heart is an oculus with a well, maybe a good thing or maybe a portal to the realms of the old gods. I’ve converted it into a missile silo. Because if you’re the hero that makes me the bad guy.