Did you ever try to design your dream home?
As a child, I built forts like it was my job. I remember using blankets and cushions, pool towels and deck chairs, anything that could and would allow me to make a little sanctuary of fun and creativity was going to be claimed and utilized for fort-awesomeness!
What about as an adult? Do you still want a trap door or a secret room or lair like Batman? I do. What about a rooftop garden to lounge in? Or a slide from your second story bedroom down into a pool? The list of amazing ideas we think of as kids goes on...and SOMETIMES those same kids get older and don't forget.
Here's a list of some cool designs that are possible if you just take the time to think them through and do some planning! Get older, but never "grow up!" Use that imagination!