I'm standing naked on Platform One of Northern Japan's Kamisuwa Japan Rail train station. The photographers from Playgirl magazine haven't yet arrived nor, for that matter, has my agent to talk about that new advertising campaign for Calvin Klein briefs. What do you mean they're not interested?

Lest you need reassurance, I haven't turned into an exhibitionist nor joined a cult dedicated to bizarre forms of public suicide. This is all quite legitimate and part of a cross-cultural experience. Amazing what you can justify in the name of cross-culture. In case you're still worried, several very conservative-looking Japanese salarymen are in the same state.I'm here trying out one of the more unusual onsen's - or hot springs baths - of the thousands that dot the Japanese archipelago. Kamisuwa bills itself as the only Japanese hot spring located in a train station.

Sometimes cultural comparisons are helpful when bridging two worlds. In this case they're not. I shudder to think what manner of deviants, perverts, evangelical reformers and sickos would show up if Amtrak offered free baths on station platforms in Newark, Boston or Philadelphia. Let's not even talk about New York.

Or, for that matter, what the congressional debate would sound like the next time Amtrak went to renew its subsidies. What do you mean community tubs are a waste of money, Newt. C'mon, it's fun.

Not that station bathing is everyday stuff in Japan, either. The sliding door to the onsen has opened several times as curious souls glance in to see just what a station bath looks like. Most are pleasantly surprised. But while it's still unusual in Japan, it's not weird. Journalistically, the dog is still biting the man, not the other way around.

So what's it like? Though small, the bath is clean, functional and even - dare I say it - picturesque. The feat has been accomplished by erecting walls in a small area at one end of Platform One between a ticket gate and the lost and found. The bath fits about six people and is screened in with bamboo. There's a tiny shelf near the entrance for shoes and a small dressing area. The bath itself is lined with dark rock walls complete with plants and a small waterfall.

On my way in I catch my reflection in the mirror. Fortunately no one else is a dead giveaway for Charles Atlas either. As I ease into the burning water, I run through the usual routine. I've already washed - Japanese baths are for soaking only - and now try and get my body used to temperatures better suited for cooked lobsters.

In the old days, the Japanese used hot baths as a form of birth control. It's not terribly difficult to see why as the initial pain sets in. Then again, with the population density of this country I guess it didn't work too well.

Before long all my nerve endings have died and I'm able to lie back and relax. Now comes the payoff. This overworked, overstressed country has got this right. Very, very right. As the heat seeps through every muscle and bone in my body, I find I can barely stand, I'm so relaxed.

For hotel owners in Japan, an onsen is a ticket to financial health. Towns hire oil drill rigs from Canada and the United States to search for hot water. One Tokyo restaurateur recently made headlines when his 30-year, $1.5 million

dream of finding a hot spring in Tokyo paid off after hiring a crew to dig 4,200 feet below ground.

What's all the fuss about taking a bath? Each onsen has its own charm. Some are beside beautiful rivers, others have a long history, still others have special mineral properties or views of Mount Fuji.

But only one lets you wear your birthday suit a mere three feet from the hordes of commuters plodding along to their next train. "Departing on Track Three will be the 3:58 bound for Tokyo's Shinjuku Station," drones a nearby loudspeaker.

The cost of using an onsen ranges from a few dollars for the public varieties - or free here in Kamisuwa if you have a train ticket - to hundreds of dollars at some of the more famous resorts.

Japan's love of bathing goes back generations. The ancient chronicle Nihon Shoki records people journeying long distances 1,000 years ago to take advantage of their curative powers. Now with improved transportation, marketing and a huge rise in stress, those numbers now top 143 million visitors annually.

Traditionally the bathhouse was often a place to unwind after work, gossip and scrub your friends' backs. Because everyone was naked without regard for rank or wealth, the concept of hadaka no tsukiai, or naked companionship, was

nurtured, says Scott Clark in his recent book "Japan: A View From the Bath."

Japan's bathhouses also reflect social prejudices. One hotel in Koromo, a town in Nagano where the 1998 Winter Olympics are being held, was recently chastised for posting "no foreigner" signs. This mirrors a 1992 controversy in Kofu City, Yamanashi Prefecture, that saw gaijin barred for fear of AIDS.

Today, most people see it as a great way to relieve tension. Some offer more sophisticated arguments on its curative powers. As your peripheral veins expand, your circulation improves allowing oxygen and nutrients to flow throughout the body and washing away waste. If you ask me, it just feels good.

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