Garden Structures

We're on the look out for simple, sturdy designs for garden structures that would fit in the TPL gardens. I ran across this site on a Google search: http://www.grandiflora.pro/cool-pics/structures-bridges-and-follies.
Here's one that I think could be scaled down to for different purposes. 

But I really like the idea of follies, something for garden decoration but suggesting another purpose, like a mini-castle or this stump cave.

Whoa. Googled some more. Folly fanciers. Huh. Post ideas that might fit in at the TPL gardens.