Deep in the bowels of the Hyatt Regency Hotel in Kyoto there is a room containing a pair of large, square baths filled with the dry, fermented powder of the Japanese cypress (hinoki) tree. And me, wearing nothing but black disposable underpants and a white hairnet.
The Riraku spa attendant bows politely and motions for me to enter the right-hand bath, which she has prepared by digging out what looks suspiciously like a shallow grave. I clamber in, lie down and am covered from head to foot with what looks and feels like warm sand.
This is Kosoyoku, a dry bath made from trees grown in Yoshino in Nara Prefecture. It seems there are some things in the hinoki called phytoncides that are supposed to have strong stress-releasing/calming effects.
What isn't in doubt is that, mixed with extracts from other plants, vegetables and fruit, the natural enzymes in this mulch stimulate fermentation and generate heat of 65 to 80 degrees. Which means it's bloody warm in here – an effect compounded when the attendant asks if I want to take the extra step and have the sand cover my face, too. Some people, she says, find it too claustrophobic.
I take the plunge, which consists of having another hairnet placed over my face and sand piled on top of that, leaving just the nose and mouth free.
The Hyatt Regency sits behind a big stand of bamboo in Higashiyama Shichijo, a verdant suburb of Kyoto which also boasts the Kyoto National Museum and the impressive Sanjusangen-do Temple with its 1000 life-size statues.
The hotel, which opened in 2006, isn't much to look at from the outside but this low-key first impression is in stark contrast to the interior, which was designed by Takashi Sugimoto from Super Potato, an eminent Japanese interior design company.
The foyer is a large open-plan space of white, brown and bronze. There's a reception desk to the right, a series of interlocking Tetris-style sofas and the hotel's main Grill restaurant and breakfast area off in the distance – all drawn together by a white ceiling fretwork of interlocking geometric patterns.
The elegant simplicity creates a soothing blend of the traditional and the modern – an aesthetic which extends to the guest rooms, where simple white walls and all the usual mod-cons contrast with the bright pop of headboards made of colourful old kimono fabrics (some of which are hundreds of years old).
Meanwhile, down in the spa, things are hotting up. I am deaf, blind, sweating and idly trying to think how to describe the light, lemony-yet-woody smell when the attendant begins to disinter me. My 15 minutes (that's all you get due to the heat) are up and I emerge from the bath like some giant claggy earthworm pulled alive from a rotting log.
The difference? I'm not squirming so much as hanging limply like someone who's had all his bones removed. I am so relaxed that the spa attendant could hang me from the back of the door.
Keith Austin was a guest of Inside Japan Tours and Qantas.
Qantas flies direct from Sydney to Osaka's Kansai airport three times a week. Flights from Melbourne and Brisbane go via Sydney. See qantas.com The shinkansen (fast train) from Osaka to Kyoto takes about 15 minutes for ¥1420 for an unreserved seat. See osakastation.com
Inside Japan Tours chooses hotels based on the individual traveller's needs and budget. The Hyatt Regency Kyoto is a 187-room five-star hotel just outside the centre of Kyoto. The 15-minute Kosoyoku bath at the Riraku spa and fitness centre costs about ¥8000 a person.See hyatt.com