IF A GROUP OF PEOPLE sat around fueled with bottles of wine and buckets of caviar and tried to build a mental picture of what an embassy residence should look like, they would have a hard time exceeding the opulence of the Turkish Embassy.

The structure rises like a castle in the air at 1606 23rd St. NW on the corner of Q Street. With a limestone eminence dominating its very visible site since 1915, the mansion is perennially on the embassy tours. This year, to benefit Goodwill Industries, it will be one of seven embassies open to Goodwill tour ticket holders from 1 to 5 p.m. Saturday.

The architect of this marvel was George Oakley Totten Jr., who in the early part of the 20th century designed a dozen or so major mansions in Washington, including many of the 16th Street embassies developed by Mrs. John Henderson. His only rival to the title of embassy architect par excellence is J. H. de Sibour, who worked in the same period and designed the French Embassy residence, also on this year's Goodwill tour.

In the splendid book of the Commission of Fine Arts, "Massachusetts Avenue Architecture, Volume I," architect J. L. Sibley Jennings Jr. describes the building as "electically combining neoclassical elements of 18th-century Europe with 15th-century Italianate details." That's putting it mildly.

Totten lavished the facade with every accountrement of a proper palace: semi-circular drive; glass art nouveau marquise with glass panels ornamented with palmette filigree; tall columns, pilasters, balustrades - almost every sort of embellishment architecture had to offer at the time.

Inside, Totten laid on gold-plated doorknobs, heavily carved beams, embroidered brocade walls, a minstrel's gallery, a ballroom with a stage, a conservatory and a loggia, a pillared drawing room, tall marble fireplace mantels, an ornate elevator, 12 or so bedrooms, parquet floors, ornate plaster work and even a swimming pool (alas now used for storage) in the basement.

Totten designed the house for E.H. Everett, the man credited with inventing the crimped Coca Cola bottle cap. (Earlier Totten designed what was then the American Embassy in Turkey and a mansion for the Sultan Abdul Hamid.) The house, which took five years to build, was rented to the Turkish Embassy in 1932 and bought by the Turkish government in 1936.The Fine Arts books says the original cost estimate of the house was $150,000, but other estimates of the final cost are at least double. The Fine Arts Commission study, however, states that the Turks paid $402,000 for it in 1936.

The wife of the present Turkish ambassador, Mrs. Melih Esenbel, says in the late '60s the Turks spent about $28,000 on repairs and it takes another $15,000 or so a year to maintain the embassy, "I have found," she says, "that if you keep the roof and the basement in good repair, all else is possible."

The mansion has held parties for 3,000 without even groaning, according to newspaper reports during the Everett's tenure.The ballroom alone will hold 130 people, seated on elegant gold-painted art nouveau-style bentwood ballroom chairs. (For some years, the embassy had to rent chairs at $2.50 per for its frequent musicales. One day Mrs. Esenbel found a mound in the attic covered with a tarpaulin. Underneath were more than 100 antique ballroom chairs. Since then, she's used her rental allowance to have them repaired and reupholstered.)

Engraved invitation in hand, the invited guest is deposited by his chauffeur-driven limousine at the portecochere. The guest walks through the marble-floored (what else?) foyer, flanked by the game room, now the ambassador's office, and the library, and up the ceremonial staircase, passing the minstrels' gallery with its enormous head of Ataturk and into the immense reception hall, suitable, one might think, for holding a receiveing line for all the peoples of the earth.

To the left is the drawing room, a rectangle with a triangular alcove. The alcove is separated from the main room by both columns and pilasters. The chandeliers shimmer with a fall of crystal pendnts. Here are ornate French furniture and objects d'art, and the remarkable collection of Ambassador and Mrs. Esenbel of photographs of the American Presidents and their staff members since Harry Truman.

The Esenbels have served at the embassy three times. When Esenbel was a young diplomat in the late 1940s, the then-ambassador, a bachelor, asked Mrs. Esenbel to serve as his hostess. "He used to always give three dinner parties in a row - I understand now why, because the flowers will last for all three and the house is all ready. But it was hard on me, with two small children, to have babysitters three nights running."

To the right is a hall which passes by the large dining room, with Mrs. Esenbel's collection of Turkish copper pots and the heavy dining room furniture original to the house; the sitting room with its relief-carved marble mantle, and mirrored curio cabinets; and the magnificent ballroom doorways pierced with a curlicue of carved ornamentation.

The ballroom at one end has a circular stage embellished with fluted columns. The walls are covered with elaborate woodwork and topped with gold thread damask. Mrs. Esenbel said that originally the ceiling were all covered with the Persian-style damask, but the ball room sections are all that have survived.

Between the ballroom and the dining room is the fanciful conservatory with its practical white marble floor for Mrs. Esenbel's lavish plants. Again the doorway is as imaginative as Totten could devise, and that of course is something. The doors, actually gates, are made of cast iron which blooms into acanthus sprays and blooms. There is a matching settee. The oriole window topped with a dome is leaded with colored representations of grapes. The other window also is of stained glass.

The Esenbels, when they aren't giving their customary three or four parties a week, usually relax upstairs. They have a comfortable sitting room, with a table for breakfast and a television set. It opens onto the loggia where Mrs. Esenbel gardens.

On the third floor are rooms for the security guard, the cook, and the two male servants one who has his wife and two sons with him. In the basement is an apartment for the upstairs servant and her husband.

In a sub-basement is the swimming pool, a wonderfully elaborate affair, according to Mrs. Esenbel. "But it has never been used as far as I can remember."

Other embassies on the tour this year, in addition to the Turkish and French, are those of Burma, Egypt, Great Britain, Romania and South Africa. The $9 ticket includes the price of a shuttle bus. Tickets are available at the participating embassies, major hotels and from Goodwill at 1219 K St. NW. For information call 638-5050.