Neither is there much to support the myriad other health benefits salt grottos purport to offer.

Actually, quite a lot of what clinic manager Grace says about the health benefits of the salt grotto doesn't bear close scrutiny.

I am standing in the Adalex Clinic's recently-opened "salt grotto."

It has indoor and outdoor pools, salt grottos, Finnish sauna, and 13 treatment rooms, where therapists use Swiss products made from local plants.

The spa: This intimate spa, tucked away in a historic hotel, offers traditional and holistic treatments, with five treatment rooms, including herb sauna and salt grotto.

The treatment is widely used in Eastern Europe and Russia , where people with chronic breathing disorders often spend two to three hours per day in underground salt grottos.

Actually it is, because for many years it has been standard practice in Eastern European countries for patients with respiratory problems to be prescribed sessions in subterranean salt grottoes.

The emphasis was on luxury, with the Himalayan salt grotto in the spa, the botanic garden winding toward a rooftop pool, the Michelin chefs instead of all-you-can-eat buffets.

Work through the Herb Sauna, Themed Shower, Ice Fountain, Crystal Steam Room, Salt Grotto and Foot Baths.

And there is a Himalaya salt grotto designed for those suffering respiratory problems, which is "a naturally ionised space absorbing the excess of electromagnetic waves and giving off beneficial negative ions".

The procedure: After 45 minutes in the thermal suite, testing the sauna and the salt grotto, Spy had the 30-minute aromatherapy back massage and a 60-minute facial, with ginseng toner and papaya enzyme peel.

While it may sound like bunkum (OK, it definitely does sound like bunkum), in Central and Eastern Europe they have been using salt grottos - both natural and artificial - for donkey's years.

Meanwhile, Norwegian's forthcoming ship, Breakaway, includes a two-level health complex with a salt grotto (to alleviate respiratory and skin ailments), a dedicated room for spinning classes and a spa (above) offering services like acupuncture, teeth-whitening and Botox.

In addition there's a salt grotto, 20-metre pool - heated to 29C, I found it too cold - and, most impressively, an open-air pool where guests can recline on bubbling waterbeds while taking in an unimpeded view of the surrounding peaks.