Peter Wing wanted to build a barn with two silos. When they began building it, the structure looked like a castle and so he said, why not? Wing ended up spending 30 or so years building an actual, full-fledged castle!
An amateur documentary by Rachel Connolly at Squigglebooth: Link - Thanks Ajit!
I've got some photos and comments about it on my blog, and there's a Roadside America article on it.