big-bash birthdays; _These days, even those out of _single digits are celebrating on a grand scale.

Byline: William Norwich

Lately it has been one big birthday bash after another, from the Olsen twins' twenty-first at their home in Los Angeles, with friends such as Kirsten Dunst and Joaquin Phoenix, to Marella Agnelli's high-society eightieth in Rome, Peggy Siegal's meritocratic sixtieth in New York, and gallerist Jeanne Greenberg Rohatyn's fortieth, for which her financier husband, Nicolas Rohatyn, not only took over the Four Seasons restaurant but also presented her with some dozen important new artworks he had commissioned to commemorate the occasion. Crown Prince Pavlos of Greece celebrated his own fortieth with an angels-and-devils-theme fancy-dress party (Americans say "costume party") for about 200 family and friends at home overlooking the River Thames in London. A tent on the lawn was filled with ice sculptures and performers towering on stilts; the main attraction at dinner was veal burgers with foie gras, and disco dancing continued into the wee hours. The prince and his princess, Marie-Chantal, wore costumes designed by Jean Paul Gaultier, but Naomi Campbell rustled up her wings and halo herself. Pavlos's younger brother Prince Nikolaos dressed in formal black tie, with a decided twist: The left side of his handsome face was painted devil-blue, and one freakishly real-looking red horn crowned the top of his forehead.

More grand events will be pitching their tents, so to speak, in the coming months.

Gwyneth Paltrow is 35 on September 27; Hillary Clinton turns 60 on October 26; Julia Roberts will be 40 two days later; Ivanka Trump will be 26 on October 30; and Caroline Kennedy Schlossberg is 50 on November 27. We may not read about their parties in the newspapers, but raise high the birthday candles because these leading ladies are unlikely to vote against any jollification on their big days. As I type, Cynthia Rowley is preparing to rent Disney World's Typhoon Lagoon, the huge water park, where she and her husband, Bill Powers, can go surfing to celebrate his fortieth at the end of September; and financier Boykin Curry is finessing plans to occupy Joe's Pub in New York for the birthday of his wife, interior decorator Celerie Kemble, on October 18. "The timing of my birthday is always very conducive to having a Halloween party," says Ivanka Trump, remembering her twenty-first, when she dressed as Waldo from the book Where's Waldo? (Five years later she still isn't sure why Waldo, but the memory is wonderful nonetheless.) This year she is thinking she may skip the inevitable theme birthday and take a few friends to Atlantic City or Las Vegas, where the Trumps have real estate interests.

On October 2, just a few weeks after she arrives in Manhattan to begin attending college at New York University, the actress Camilla Belle will celebrate her twenty-first birthday.

"I will be a newbie in town, so hopefully I will know some people to throw a little party with by then," says Camilla. "My mom always gave me the most amazing and elaborate parties, so I've had good experiences. I threw a surprise birthday party for her when I was thirteen, which ended up a disaster because I invited all these people who I thought were my mom's friends . . . but actually weren't. So I guess the best advice," she ...