Gather all the blankets from the cupboards and beds, all the cushions from the lounge and pillows from every ones beds and drape them over a couple of chairs and a table/bed and VOILA you now have your very own bears cave, knights castle, pirate ship, lions den, refuge from mum, a place to sit and eat the goodies you snuck from the kitchen cupboard and drink cordial you know your not usually allowed, a place to rest, a place to tuck your teddies in to bed and hide from the world.
It must be dark, it must have multiple levels and entries, windows, doors, beds, tables and chairs to eat from and most importantly mum can not possibly be allowed to see in. The only time she is allowed to enter 'the cubby' is when she brings snacks and drinks.
Each day the cubbies in our house are getting more and more elaborate, the last one had a slippery slid an entry for dragons and consumed three quarters of Myles' bedroom. I LOVE IT.