THis is where I may be of some help about the bunker , I spent 25 years in an industry , whos job it is to either hide things in plain sight or to make a fantasy world in a said space . I would turn that entire bunker area into a rock formation , do a good professional job , sense people have already seen it , I would tell them that you are just getting started , and that is just a maintenance room for the plumbing and electrical , as well as storage for chemicals , etc. Design the rock work to have a resurculating pump ( they are actually quite small , but most people dont know that ) and build a waterfall element with small pond at the bottom built into the rock ……this is a very common landscape element that people have seen a great deal ……it will also up the property value . You will need steel ( # 3or 4 bar ) , drill directly into the top and sides of the bunker , bend the shape , and make a cage grid , 1 foot squares approx . , Then steel lath to hold the cement to the structure ( lath UNDER the cage , not on top of the cage ) then cover with cement for a structure coat covering all the rebar , dont forget to rake or score the surface , this makes it easier for the finish coat to stick , you want it 2 inches thick min . so tie your lath accordingly . Then the fun part , the finish coat , cover in again , not all at once , and hand carve your rock to the desired look , when its all done paint it . You have now done several things at once , you have upped your property value with an attractive rock and water element , reinforced the bunker , and made the bunker go away in plain sight . I would also do a few planter pockets into the rock , and plant around it and add some dead fall trunks for more of an illusion . Many many other things I could tell you but it would be a book , I can and have made things so real , that you wouldnt know it was fake if you were standing on it .