The Royal Pavilion at Brighton in England is the sort of castle a small child might build out of the sands of Brighton on a clear summer day when all things seem possible and dreams soar like a balloon. The pavilion's great domes topped with spires, its tall arched windows and elaborate tracery make a fitting palace for a fairytale monarch.

Brighton Pavilion is, by any definition, a folly . On the outside it's style is a romanticized hindoo ; on the inside it's far, Far Eastern, and the whole is a rococo roll that became the Regency period. Brighton Pavilion was built from 1787 to 1822 as the pleasure dome of George IV, first as regent and later king - and at all times a man to whom the luxuries of life were necessities.

A taste of Brighton is being offered through May 22 at Cooper-Hewitt, the Smithsonian's National Museum of Design, which is housed in the former Andrew Carnegie Mansion. Eight rare pieces of th pavilion's original furniture and decorative objects now customarily housed at Buckingham Palace are on loan from Queen Elizabeth II, including an Indian sandalwood chair mounted with engraved ivory and carved with monstrous heads on the back and acanthus leaves on the knees with palmettes flanking the feet; a sideboard veneered in rosewood and satinwood with gilded carved dragons; and a set of enameled bronze candelabra in the form of a Chinese lady, matching the Chinese drummer boy clock.

The show was suggested by/one of the prizes of the Cooper-Hewitt holdings: 87 drawings of the interior decoration of Brighton Pavilion by the firm of Frederick Crace. On loan from the Pavilion's own collections are 168 pieces of furniture (a pedestal lamp is made of Spode porcelain sides, flanked by ormolu dragons with a dolphin base and topped with a flower shader, architectural elements (including a silvered and painted giant serpent originally suspended from the saloon ceiling); prints and drawings, including 25 plates from John Nash's "Views of the Royal Pavilion," a contemporary book of engravings: and 33 drawings by Augustus Pugin for the "Views."

After New York, the show will travel, though unfortunately there are yet no plans for it to come to Washington. This is the second exhibit in the newly restored and opened Andrew Carnegie Mansion.

The show honors Queen Elizabeth on the occasion of the silver jubilee of her reign. It was organized with John Morley, director of the pavilion. Vincent Ciulla, exhibition designer, and Dorothy Twining Globus and Elaine Evans Dee, coordinators, are responsible for the well-done installation which highlights but doesn't overshadow the objects.

The Brighton show comes at a time when there is a swing in taste back to the romantic in decoration. For years, such extravagant fantasies were laughed at as excessive or just plain bad taste. But after years of living with purity of line, many people are becoming tired of the stripped-down, holier-than-thou look of international architecture and design. And so the pendulum swings away from the classic clean look and back to the romantic, magpie nest of fun and fantasy. Already there has been a stirring of romantic design in furniture and accessories for the home: oriental rugs from the revival of the China trade; bedspreads, fabrics and brass from India; foil wallpaper; fabric and paper wall-size murals; sheets made from museum reproductions; lush fabrics like velvets, leathers and satins; and the massing of collectibles even on apartment walls. The current show at the Cooper-Hewitt is likely to be a strong influence in pushing such "more is more" decorating trends.

According to Morley writing in the catalog, George IV (then Prince of Wales) in 1785 brought his morganatic wife, known as Mrs. Fitzherbert, to the Marine Pavilion at Brighton. (Though the marriage was acknowledged to be legal by the Pope, the king later married the royal Caroline of Brunswick.) He was a man who cared strongly for every flip of a fringe, every dart in a drapery. He hired Henry Holland to incorporate the existing farmhouse into a pavilion of Palladian design, with delicate wrought iron work as a softener. The inside was decorated in the Chinese manner in 1801, thanks to a gift of Chinese wallpaper. The interior decorations were largely done by the Federick Crace firm, which managed to hold onto the job through various architects and contractors.

Before long, William Porden and Humphrey Repton were asked to submit proposals for an oriental remodeling of the exterior. Both were rejected, but the East Indian-style circular stables domed with glass were built in 1808. Architect John Nash - closely watched by the king (who ascended to the throne in 1820) - remodeled the pavilion in the romanticized East Indian-style between 1815 and 1822, using brick covered with stucco to form porticos, minarets and pillars. Decorations were in Bath stone and cast iron was also used.

Nash wrote, "It was determined by His Majesty that the Pavilion should assume an Eastern character, and the Hindoo style of Architecture was adopted in the expectation that the turban domes and lofty pinnacles might from their glittering and picturesque effect, attract and fix the attention of the Spectator - "Of the cost, a contemporary account said, "No regular estimates were made, nor were they required and if they had been made with the greatest care they would not have corresponded with the expenditure."

Much of the inside decoration was designed by Robert Jones for Crace. Morley says it took 35 people to paint the music room. Eighteenth-century Chinese porcelains embellished with rococo ormolu were among the glories of the house. One entered through the octtagon hall with its pink, lilac and red-tented ceiling. The red drawing room was covered with dragons topped with trompe l'oeil bamboo frames. A door in the present exhibition has wood graining which upon close inspection turns out to be dragons. An elaborate overdoor (also at Cooper-Hewitt) illustrates the Indian influence. The corridor in its later decoration had ivory and sandalwood chairs reflected in mirrors upon mirrors.

The banqueting room, as Morley says, is "one of the most astonishing and exhilarating rooms in the world, the inner dome with its trompe l'oeil plantain leaves (some in three-dimensional painted copper)."

The kitchen also had great copper palms topping iron columns. The saloon was in red and gold. Best of all, Morley likes the music room, "a great lacquer box" with six huge Yung Cheng porcelain pagodas.

Since 1850 and the reign of the more staid Queen Victoria, the pavilion has been owned by the township of Brighton and used for assemblages, exhibitions and such. Though Victoria did not want the pavilion, she did want its fripperies. Almost everything that was loose, and some things that weren't, was carried away to Buckingham Palace, which also profited from the sale of the pavilion.

In 1914-18 the pavilion was a hospital for wounded soldiers from East Indian regiments. They must have thought their minds wounded as well when contemplating its wonders through their fevers. Since 1945, the pavilion has been under serious restoration, greatly helped by the permanent loan by Queen Elizabeth of much of the original furniture. Layer by layer the varnish and bronze paint of its Victorian mistreatment are bring removed - in many cases revealing the original gold leaf in restorable use underneath.

Lisa Taylor, the Cooper-Hewitt's director calls the show "Lisa's Folly," in part because she hasn't yet figured out a way to pay all its $200,000 cost, a modest sum, when compared to some blockbuster shows like King Tut, now at the National Gallery of Art. Taylor is mounting a Regency Ball in April with the hope of raising at least half that amount. (The show's catalog with magnificent color pictures, $5, and posters will also help.)

Those of us who see it, will find the Brighton Pavilion a vicarious substitute for not being born kings and queens. And surely we owe George IV some small appreciation for spending his money, if not for the general good, at tleast for the general amusement. And who's to say that luxury is not a necessity after all?