I have a male betta who once covered the entire top of his two gallon hex tank, though he usually just does one corner of it. I also have another betta who builds tall bubblenests that sometimes stand half an inch to an inch over the surface of the water, which I had never seen before. Still, they don't quite match the size in that tank as that is one heckuva bubblenest. I'm actually jealous--my females never made nests!
On a side note, I see you, too, are a fan of the old-flowerpots-make-awesome-fishtank-decor school of thought. Do you buy and break them for the tank yourself, or do you just do as I do and wait for the inevitable accident (in my case, cat-caused) to create one for you?