That looks like a lot of fun. I happen to build in mine craft with my 10yr old son and I have so many hidden rooms around that he'll get caught by this a lot LOL. Kudos to you for finding this gem.
I made a portcullis, its pretty cool. No idea what to do though as I made it inside a mountain. I added 4 rooms and a little hallway that goes into a 4-way split hallway.