Last Christmas, I got my sister a build-it-yourself medieval fort. She wasn't very happy with it, but my mother reprimanded her by saying that it isn't the gift, but the fort that counts!
For the last two weeks my kids have been building a medieval blanket fort every evening to sleep in. Many nights they also stayed up past their bedtime playing fortnight under its protective cover.
It was a night knight fort for Fortnight for a fortnight.