Air fort! Funny you should ask. I just recently bought this on a whim as a Lightning Deal because I was tired of my 7yo hauling out blankets and chairs every time she wanted to build a fort. We love it! Super easy to set up. All you need is a standard box fan (I bought one on Amazon). Kind of pricey for just some fabric, but I love that there aren't a bunch of pieces to put away/store. The convenience is worth the cost IMO.
https://www.amazon.com/dp/B077XPDBPT/
Jennifer
SAHM to DD1 (11yo) and DD2 (5yo)