Underground hidden bunkers

[dim delta]

Would you guys be able to put in hidden underground bunkers that you need to find/solve puzzles to find and enter and please don't leak where they are at just tell us how many are out there..... It would be amazing and fun to explore like old hidden underground bunkers

[hardy prawn]

I´d be happy to even build my own underground shelter.
Starting off with a small underground shed and developing it into a real concrete walled bunker