Here’s a truly glamorous idea for a pool. A sinking pool! The apparently permanent stone floor in this room literally slowly drops to reveal the pool underneath. In the raised position, you can walk on the same surface radiantly warmed from beneath. And of course, having the swimming pool convert itself into a floor makes it child-friendly too: this is not a pool that a child can fall into.
Once it is sunken it looks like any other indoor pool – as permanent as you could possibly want.