There are few things I like better in adventure storytelling than secret passages. In fact, the two middle grade novels I have in mind (one written, one started a few times but never finished) both are heavily reliant on secret passages. I think that's a dream of a lot of kids, to live in a house that has secret passages.
Did you ever see the movie Candlestick with Jodie Foster when she was a spunky kid? I can't tell you how many times I watched that movie as a kid. I want to watch it now and see if it holds up the test of time.
Walking around Old Sturbridge Village with my wife, she saw a hill in a field, most likely just piled dirt that eventually had grass grow over it. She sees it and says, "That needs a hobbit hole." Well, on one side of it is a dead and dry tree stump. And I say that there is a hobbit hole. It's beneath the tree stump and the whole thing opens up.
This causes the magnesium flash in my brain where ideas start flying up like fireworks. I LOVE secret passages. What if hobbits lived in a less friendly place than the shire? If they had hidden the doors to their hobbit holes, would Saruman been able to scour the shire as he did? They could have hidden and who would have worked the fields for him?
So this is what I want. I want underground houses like hobbit holes, but I want natural landmarks like tree stumps that no one would think twice of when they saw them, but open up to reveal the actual entrance to their home. When they're closed, it just looks like hills.
I need to figure out how to make this happen.