Jon and I happened upon the Prague main library in Old Town the other day, so we walked in, where we found this:
It's a floor-to-ceiling hollow tower of books and it looks pretty cool.
And this is what you see when you look in. It gave me vertigo, even though it's just a mirror in the bottom. There's one in the top, too, so it looks like an endless cylinder of books.
I think I should build one in our house!