The boys mill about awkwardly, occasionally batting at the black tails of their coats. The girls smooth the full skirts of their creamy white ball gowns, tugging at long white gloves. Here a hand flies to capture an errant curl, there one fiddles nervously with a string of pearls. In moments a fanfare will start the opening ceremony of the Lawyer's Ball. These debutantes and their escorts will form a procession into the ballroom of Vienna's Imperial Palace, once the seat of the Hapsburg empire. After months of practice, the young couples will be put to the ultimate test. For the first time in public, they will perform the dance that is Viennese society's lifeblood. They will waltz. From New Year's Eve until Ash Wednesday, near the end of February, the pre-Lenten carnival season called Fasching turns Vienna into a whirl of balls. On freezing black nights the imposing 19th-century buildings along the Ringstrasse blaze with lights, and the surrounding streets are filled with laughter and the rustle of gleaming taffeta and satin. Men in formal black help women encumbered by voluminous skirts emerge from cars, taxis, and horse-drawn fiacres. Cameras flash as couples mount marble steps and sweep into ornate, chandeliered ballrooms. Once inside it is easy to lose track of the century. It would be no surprise to look up and see the Emperor Franz Josef smiling benignly from the seat of honor.

For hundreds of years the Viennese have been ball-mad. In carnival season the aristocracy had their balls, and so did the professional classes, from doctors and lawyers on down to butchers and bakers. But the true golden age of Vienna's balls arrived with the waltz.

Until then, it was considered scandalous in polite society for a man to hold a woman while they danced, let alone turn her. But while the aristocracy performed intricate minuets, the peasants were whirling, arms wrapped around each other, in exuberant three-beat-per-bar folk dances like the Ländler. This folk music found its way into compositions by Mozart and Schubert, and by the time of the Congress of Vienna in 1815, rollicking folk dance had become the rage of the court. Gradually, it evolved into the elegant, gliding waltz, taken from the word waltzen, meaning "to turn."

Every year at the stroke of midnight on December 31st, Johann Strauss Jr.'s 1867 "Blue Danube" still is played on radios all over Austria. It may not be the country's national anthem, but it is certainly its theme song. Even the more free-form of today's nearly 300 balls are bathed in nostalgia for an empire extinguished by the Great War. The aristocracy may be gone, but the guild-sponsored balls continue. Some of them are world famous, like the huge Opera Ball, or the Imperial Ball, which ushers in the season on New Year's Eve. While they're open to all, they're expensive to attend, and once inside, a parched dancer might find that a glass of Champagne costs $30.

But in Vienna, there's a ball for everyone, from the elegant formality of the Lawyer's Ball to the commercial chocolate-fueled revelry of the Bonbon Ball. For the more bohemian, there are a couple of arty anti-balls. Last year social activists even staged a Homeless Ball.

FACING THE MUSIC    Every young person in Vienna who expects to dance in the opening sequences must spend at least a few months at one of a dozen dance schools learning the intricate steps to the classic waltz melodies. It's not easy.

At the Tanzschule Elmayer, next to the Spanish Riding School, a mix of Viennese society's offspring, hopeful climbers, and out-of-town visitors gathers in two hardwood-floored practice rooms. The Viennese Waltz is a series of fast, dizzying turns. Because the ballrooms are crowded (at the legendary Opera Ball, 7,000 dance till dawn), each couple maneuvers in an approximately 10-foot circle while slowly progressing around the floor. Aside from the Viennese themselves, only the most ambitious ballroom dancers take on the Viennese waltz. The schools make even more sense when you realize that the competition to become a debutante at one of the more famous balls hinges not on social background but on a young woman's ability to waltz.

Elmayer students attend weekly classes for a year. They're awarded bronze, silver, and gold stars, and a debutante should have at least a silver star. There are also seminars in etiquette. As in the days of the Emperor and his court, the Viennese still address one another with excruciating formality (Herr Doktor, Herr Professor, with their wives sharing in the title as Frau Doktor, and so on).

Not far from the amusement park made famous in The Third Man is the apartment where Johann Strauss Jr., composed "The Blue Danube." It's now a museum full of Strauss memorabilia, a little short on thrills but containing paintings of several balls, ball favors, jewelry, and some period gowns that drive home how little formal dress has changed in the past century. Men still wear tails, and though the ladies' bodices may be less fussy, their skirts are still made of yards and yards of gathered silk that's often covered in bows.

In the United States, balls are most often charity events for the elite. Unless you're a member of high society -- or bound for a senior prom -- you're not likely to own a formal gown. But Viennese of all social classes go to at least one ball, and usually more, during the season. Viennese men own their own dinner jackets and tails, and a Viennese woman is likely to possess one or more of the anachronistic gowns that give the balls their glorious air of nostalgia. After a couple of balls you start to recognize the dresses. They're like houses in a development, each a slightly different model but adhering to a theme, and the same fabric pops up time and again.

SWEET DREAMS    A gigantic pink blow-up elephant bobs outside the wedding-cake facade of the Konzerthaus, by the Ringstrasse. Inside, on a Friday night in late February, the Bonbon Ball is getting off to a start, with good-natured jostling in the lobby as men in animal costumes hand out candy samples, which ballgoers stuff into the cotton shopping bags handed out by a coffee manufacturer. Men in tails or dinner jackets grin, revealing teeth stained with chocolate. Long-gowned young women are giggling, handing bags bulging with sample bonbons to the coat-check women, touching up their lipstick in pocket mirrors.

At this ball the debutantes are preceded by a raucous tropical floor show. Overhead, huge balloons float amid the chandeliers. At midnight they are punctured, and chocolates rain down on the celebrants. A Miss Bonbon is selected and awarded her weight in candies. Even before, the anterooms are hot and heavy with smoke, and rock-and-roll drowns out conversations. Ties have been loosened and some of the gowns have begun to wilt, but the couples lounging around the tables are only getting a second wind.

The Viennese waltzes in the main ballroom (actually the concert hall, from which the seats have been removed) are interrupted periodically for contests and door prizes. "I come every year, but I never win anything," shrugs a portly 60-ish candy manufacturer gazing down from a box seat into the sea of milling dancers. A cheer goes up as the orchestra starts again. The businessman grasps his wife's hand and they descend to the floor, where they begin effortlessly waltzing, her garnet skirt floating behind her.

All these earthy festivities are a far cry from the formality of the Lawyer's Ball. The opening ceremonies that night seem to go on forever, an endless parade of lawyers and law professors and government dignitaries passing between the rows of nervous debutantes and their stone-faced, damp-browed escorts. Finally one of the girls sinks to the floor in a bubble of white satin. She's helped to the side and revived with sparkling mineral water and whispered words of encouragement, then returned to her place in line just as the first waltz begins.

The couples face one another self-consciously. A few of the girls glance around in terror. They step side to side, then the introduction segues into the rhythms of the waltz and they begin turning with growing confidence, a sea of black and white. Parents beam from the sidelines. Then the velvet ropes are removed. Couples pour onto the dance floor, the women's gowns like a jumble of jewels tossed into the black-and-white waves.

On three sides of the main ballroom stately halls open onto other, equally large dancing areas and small overheated buffets. Eight orchestras, combos, and bands are interspersed through nearly 20 rooms, all filled with elegantly garbed Viennese-and one red-faced Scotsman in a kilt. A woman in an emerald gown, her bouffant skirt covered with velvet bows, fans herself as she walks arm in arm with a woman in a stylish bias-cut dress. This must be the only place in the world where haute couture is the wrong thing to wear.

In the main ballroom an old man and a bored-looking young woman take the floor. The room has cleared a bit but is still crowded. A waltz begins. The old man shuffles his feet. The girl looks off into the distance, swaying. It seems as if even those too old to dance find the waltz impossible to resist. This must be his granddaughter indulging him. Then, suddenly, the old man gives her an abrupt nod and they take off, spinning with such skill and verve I can't help but see them as the two faces of the ball -- the old man who's waltzed at hundreds of balls, and the shining-haired young woman who has a lifetime of silk gowns, ball seasons, and Strauss waltzes opening up before her like a scroll.

Shortly after midnight we reclaim our coats and start back to the hotel, strolling by the Hofburg and pausing one last time to admire the ornate gate. Laughter from late-night revelers echoes through the arcade by the Spanish Riding School. Across the Kartnerstrasse there's a sausage wagon. We join a street cleaner on his break and a couple fresh out of a nearby disco, and no one seems to find it the least bit strange that two people in formal dress are devouring mustard-laden sausages on the street.

After all, this is Vienna, where sooner or later, everyone goes to a ball.