In Istanbul you absolutely must have a bath," a friend insisted before my recent trip to Turkey. Rather odd advice, I thought, until it became clear that my friend was recommending a visit to a hama m, a Turkish bath house.

And after an uncomfortable overnight train ride from the Greek border, followed by a full day of sightseeing in Istanbul's grimy pollution, I was ready to spend several hours luxuriating in one of the famous baths. The experience proved to be a somewhat exotic version of a visit to a modern health club, complete with steam room and personal masseuse, but without the obligatory aerobics.

Although guidebooks written by westerners in the 19th century often described the Turkish bath as a curious oriental custom, its origins do not lie in the East.

When Constantine I founded the new capital of his empire on the shores of the Bosporus in 330 A.D., he brought to it the social and cultural traditions of ancient Rome, including public baths. One thousand years later, Constantinople fell to the Ottoman Turks, who absorbed the custom into their culture, where its popularity flourished well into the present century.

For Turkish women, bathing was once a social as well as a hygienic ritual. Until the establishment of the modern Turkish state in 1923, they lived under the strict Moslem rule of purdah, cloaked publicly behind heavy veils and confined privately to the companionship of immediate family. The weekly visit to the hama m, where the better part of the day could be spent exchanging news and gossip, provided a rare opportunity to visit with women outside the family circle.

In 1717, Lady Mary Wortley Montagu recorded her impressions of a visit to a hama m in Istanbul, where she found more than 200 women relaxing after their baths. They lay on sofas covered with cushions and rich carpets and were engaged "some in conversation, some working, others drinking coffee or sherbet, and many negligently lying on their cushions while their slaves (generally pretty girls of 18 or 19) were employed in braiding their hair in pretty fancies."

Between slave and mistress there existed no distinction in dress, the Englishwoman noted, "all being in the state of nature that is, in plain English, stark naked." As she arrived at the hama m attired in a riding habit, Lady Montagu might have felt slightly overdressed. When pressed to enjoy a bath herself, she opened her shirt and showed her stays, which she stated "satisfied them very well; for, I saw, they believed I was locked up in that machine and that it was not in my power to open it, which contrivance they attributed to my husband."

The introduction of modern plumbing into private homes in the early 1900s marked a decline in the number and use of public baths, although a few can still be found in the older quarters of Istanbul.

Encumbered by neither husbands nor stays, two traveling companions and I decided to visit one located a convenient 10-minute walk from Topkapi Palace in the center of the old city. A small sign outside noted that the hama m had been in use for more than 300 years and listed several famous Western patrons, including the composer Franz Liszt, the Kaiser Wilhelm II, as well as Florence Nightingale.

The latter's name greatly cheered one of my companions, a nurse from New Zealand, who had been concerned about sanitation standards. But if it had been good enough for the founder of her profession, she reasoned, it would probably do for us.

We first tried the main door, which led directly into the men's bathing quarters, where the arrival of three females -- obviously foreigners -- caused some embarrassment. An attendant directed us back outside and down a narrow side street to the women's hama m, whose English-speaking proprietress welcomed us graciously. A price list was presented ranging from a $3 "single" bath to a $15 "deluxe"; without quite understanding the difference in their descriptions, we compromised on a $7 "complete."

The first room of the hama m was a great round hall, perhaps 100 feet high, topped with a domed roof. Around the walls were small compartments with glass doors. We were shown to one of these dressing rooms, furnished only with narrow wooden couches, where our clothes were safely locked away for the several hours we spent in the bath.

We emerged from the dressing room wrapped in oversized saffron-colored towels and wearing wooden platform sandals with high stilted heels. Wobbling precariously, we followed the proprietress through a dark, low passageway and into the main bathing chamber.

The enormous circular room, constructed entirely of white marble and covered with thin curling clouds of steam, was flooded with sunlight streaming through windows in a dome high overhead. Two parallel marble steps, the lower one set a few feet above the floor, ran around the entire circumference of the walls; above them, spaced several yards apart, stood numerous stone basins, fluted like huge cockleshells. Water flowing from ornately carved fountainheads filled the basins and overflowed onto the floor into little channels or drains. As in the old Roman baths, steam was produced naturally from water flowing over warmed stone. The temperature was not overly hot but designed to gently open the pores of the skin.

We were each led to one of the basins, and our towels and sandals were removed. Seated on the low steps beneath the fountains, we were given saucer-shaped scoops to douse ourselves with water from the basins as we waited our turn to bathe.

The center of the room was covered by a large, round marble platform, raised slightly above the floor, on which the bath attendants were finishing the ablutions of several women. We later learned that these bathers had opted for the $15 "deluxe," which proved to be nothing more than a double version of the $7 "complete." (We also discovered that the $3 "single" was basically a do-it-yourself operation with only soap and towels provided.)

For us, the "complete" was just right. After a pleasant interval relaxing in the warm steam, we were escorted to the bathing platform by our individual attendants and seated on thin rubber mats. First our skin was scraped from neck to feet with a rough camel's-hair glove to remove the top level of dead skin. Administered with long, sweeping strokes, this procedure was mercifully quick. After being dashed with a bucket of warm water, we lay on our backs while being covered with soapsuds and scrubbed with soft natural sponges that felt wonderfully soothing after the rough camel's hair. Turned on our stomachs, our backs were similarly cleansed and rinsed with water from brightly colored plastic pails that the attendants filled from the fountains.

Clad only in narrow black G-strings, these women resembled Japanese wrestlers, their girth greatly exceeding any such polite euphemism as "plump." They talked and laughed among themselves or hummed softly as they kneaded our skin, addressing us now and then in their few phrases of broken English. A lengthy massage followed the first sudsing and the strength of their arms and hands left no taut muscle or knotted nerve anywhere in the body. Their movements were firm and smooth without the pounding or jerking associated with other types of massage. Thoroughly limp, we were left to doze awhile, the enormous room curiously quiet except for the play of water from the fountains. We awoke to another lathering and scrubbing with soapsuds and a final cascade of cool water from the plastic pails.

Afterwards we resumed sitting beneath the fountains while the attendants, kneeling on steps above us, shampooed our hair with such vigor our scalps felt as if they, too, had been scoured. More buckets of water were emptied over our heads, and our hair was quickly towel dried and untangled with wide-tooth combs. Finally, the attendants smoothed the bottoms of our feet with large flat pumice stones and, the "complete" completed, we felt sleek and soft from head to toe.

A new group of bathers arrived and we were left alone to resume leisurely scooping saucers of water over our perfectly relaxed bodies. When we felt we could no longer stay awake, we donned our towels and sandals and returned to the dressing room. There the proprietress exchanged our wet towels for dry ones and served us little glasses of hot, sweet tea, which we drank while stretched across the narrow couches. "All it really lacked was a rubber duck," yawned one of my companions as we drifted off to sleep.

Later I was to meet another traveler en route to Turkey who asked what to do in Istanbul. After extolling the splendors of Topkapi, the beauty of the city's mosques and the delights of an afternoon boat ride along the Bosporus, I gave my best advice: "And by all means, take a bath."