Soul Music by Terry Pratchett
It was a room within a room. There was a large, heavy-looking desk on a raised dias, with a leather swivel chair behind it. There was a large model of the Discworld, on a sort of ornament made of four elephants standing on the shell of a turtle. There were several bookshelves, the large volumes piled in the haphazard fashion of people who are far too busy using the books to ever arrange them properly. There was even a window, hanging in the air a few feet above the ground.
But there were no walls. There was nothing between the edge of the carpet and the walls of the greater room except floor, and even that was too precise a word for it. It didn't look like rock and it certainly wasn't wood. It made no sound when Susan walked on it. It was simply surface, in a purely geometrical sense.
The carpet had a skull-and-bones pattern.
In the distance, towards the wall of the greater room, the metaroom or whatever it was, there was a suggestion of... something. Something was casting complicated shadows, too far away to be clearly seen.