The Way We Live Now: Spa pavilions

If you can find a bigger Higher Purpose for a room, you can add value to everything: to your house, to your life – you're an altogether more evolved person. It's worked for kitchens, re-thought from utilitarian galley to main entertaining room, heart-of-the-home, all that. Or a secondary bedroom that becomes a home office and develops a rash of shelving and a mass of cable management. There'll be enough computing power to have served a Nineties City broker, and enough presentation equipment for a Nineties ad agency.

Bathrooms have been refigured and reformatted too. For the 21st-century rich, a bathroom shouldn't look like a hygienic box with a few standard fireclay and enamelled street fittings. It could be a wet-room, an integrated experience positively hewn out of really expensive stone. It could be a big smart room in its own right. But above all, it could become a spa. Spa means The Waters, it means therapy and stress management and escape. It means kindly young women from far countries padding around in flat shoes, carrying towels and scented massage oils.

Bathrooms that aspire to the condition of a spa have to be extra big. They need a free-standing bath to make the point that this is the place for long soaks and New Age experiences. And you need all that space for the rest of the kit: things stored in profligate multiples, specialist furniture for lying on. Not only bigger and better fitted, a spa room needs a sybaritic, distinctive style, or a Spartan one. The Spartan ones are self-consciously rough-hewn wood and stone combos; sybaritic ones look like the Sanderson Hotel with sheer curtains, clever lighting and soothing colours.

This urban bathroom, with its sweep of gloriously wasted space, is designed to create Altered Images and swirly-whirly moments. But unlike the conventional spa, there's absolutely no contact with the outside world here, no springs or salts, no encouraging weather. Instead, occupants will be thrown in on themselves as the natural centre of the universe. This is a room where a woman can lie around in white towelling, spending what the Duchess of Windsor called "a day on hair and nails" or, later, the brilliant Vidal Sassoon and the then Mrs Sassoon called "a year of health and beauty". Bathrooms like this are designed to provoke that thinking.

There doesn't look to be any natural light. Why should there be? This isn't the cool-as-a-mountain-stream spa. It's more the dug out from the natural clay of South Kensington at great cost variety. It's the secret refuge of one rich woman variety. There's a warm glowing quality to this bathroom. It's the delicious prelude to something. And absolutely everything says that it's for you because you're worth it.