SIXTEENTH STREET rides high, wide and handsome in a great six-mile promenade of presidents. The street begins in front of the White House as a flower-strewn path across Lafayette Park. It parades in a red brake-light line up Meridian Hill to Columbia Road, where all countries converge. Then, with confidence, it passes politely by azalea front lawns to the North Portal, Maryland's ceremonial entrance to the capital.

Sixteenth Street: Ride up it in a convertible with the top down and your head bob-bobbing along so you won't miss the antennas beaming secrets from the roof of the Soviet Embassy -- not to mention the 15 other embassy chanceries, ambassadorial residences and attache' offices along the way.

Or stroll down it, looking for the Norway maples along the sidewalks, with what's left of 536 brass plaques commemorating fallen soldiers of World War I.

Crane your neck at the acroteria (pedestals bearing statues, in this case birds, placed on a pediment) atop the mother temple of Scottish Rite Freemasonry.

Smile at the charming row of tall thin houses (each a different color, because this is 16th Street) looking like a row of ladyfingers ready for a Charlotte pudding.

Stop in a hospitable, gold-leafed, European-mannered hotel, rest your feet, eat a white-chocolate mousse.

Watch out for Richardson Romanesque entryways to lawyers' offices, great yawning mouths ready to swallow you up.

Saunter along this Road to Heaven, this Jacob's Ladder, this Path of Righteousness to 45 churches: Rich ones pushing their spires to the heavens, needles for the saints to stand on; poor ones making do with more earthbound sanctuaries in yellow brick bungalows with wide front porches.

Ponder whether Henry M. Bain Jr., consultant to the Joint Congressional Committee on Washington, was right when he said (in 1960) that the District should put up a tollbooth at the North Portal, on the Maryland line.

"In everything but name, Sixteenth Street is a grand avenue," says the American Institute of Architects' A Guide to the Architecture of Washington, D.C.

"Sixteenth Street . . . makes accessible the hills above the Washington plain. The prospect gives the street the finest setting of any avenue in the Capital," says the Commission of Fine Arts' Sixteenth Street Architecture, Vol. 1.

"Something like the Champs Elyse'es, Sixteenth Street is central, straight, broad and long . . ." wrote Mary Foote Henderson, who owned 300 lots and built 12 embassies on her paradisal path.

On March 4, 1913, Henderson got Congress to change the name to Avenue of the Presidents. On July 21, 1914, when she was out of town on vacation, Sen. Henry Cabot Lodge led the fight to change the name back.

Sixteenth Street is an architectural sampler of Washington's 187-year-history. The boulevard, like Gaul, divides into three parts:

Lafayette Square to Florida Avenue embraces the most historic blocks. Until 1890, Florida Avenue, once called Boundary Street, divided the City of Washington from the Territory of Columbia. Florida Avenue (W Street on the east side) is on the fall line, where streams make waterfalls. As Webster's defines it: "the boundary between the ancient crystalline rocks of the Appalachian piedmont and the younger, softer rocks of the Atlantic coastal plain."

Meridian Hill, whose foot is the fall line, until the late 1880s was out in the country. Sixteenth Street beyond Boundary Street wasn't even graded and paved until 1900, and then only because of the influence of Sen. John Sherman of Ohio, who owned land in the neighborhood.

Meridian Hill to Columbia Road is Henderson's own United Nations of embassies and ethnic restaurants.

Adams-Morgan to the North Portal was developed from the 1920s on, an Olympus of temples to gods both known and unknown, and a gold and silver coast of large houses on estate-sized lots.

On a cool day when fall is more than a steamy mirage, put the top down, or better yet put your Rockports on, and sashay up the avenue. This guide will go with you from Lafayette Square to Boundary Street.

The Chamber of Commerce building, between 16th and Connecticut on H, designed by Cass Gilbert, 1925, is a Classical Revival edifice, intended to echo the nearby Treasury Building. The houses of Daniel Webster and later William W. Corcoran and Thomas Ritchie were torn down to make way for it.

The house of then secretary of state Webster stood at 1611 H. Admirers had bought the house for him in 1841 but he couldn't afford to keep it up. Banker William W. Corcoran bought it in 1849 and hired James Renwick to remodel and greatly expand the mansion. Corcoran filled the rooms and the nooks and crannies with his art collection. When he bought Hiram Powers' statue "The Greek Slave," a modest nude, there were separate viewing hours for ladies and gentlemen. Corcoran's collection outgrew his house, so in 1859 he built his first art museum, now the Renwick Gallery, at 17th and Pennsylvania. The present Corcoran Gallery down the street at 17th and New York was built in 1897, after his death.

Next door at 1607 H was a house Corcoran built and sold to Thomas Ritchie, editor of the Whig newspaper "The Union." Henry Adams (who's credited with writing Democracy, the first Washington roman a` clef, as well as The Education of Henry Adams) and his wife, Marian, called Clover), rented the house while theirs was being built next door on H at 16th.

Mrs. Adams died from drinking cyanide in the Ritchie house in 1885, and the widower moved alone to the new house.

H.H. Richardson (who is credited or blamed for the bastard style called Romanesque Revival) designed the semi-attached or double houses, huge red-brick structures.

The Adams house, smaller and more comfortable, opened on H Street; the more impressive and formal John Hay house was entered from 16th. One of its "cloisonne'" stained-glass windows, by John La Farge, was given to the National Museum of American Art by James Symington, Alice Hay Wadsworth's grandson and the former chief of protocol.

The Hay-Adams Hotel was built in 1927 by Mihran Mesrobian and Harry Wardman, who regrettably tore down the Hay-Adams houses to make room. That boom year of 1927 transformed the streets of Washington, wiping out great monuments of the 19th century. The balloon burst when the stock market crash of 1929 precipitated the Great Depression.

It would have been far wiser to have kept the houses and made a hotel out of them; they would have offered far grander public rooms and perhaps as many guest bedrooms.

The Hay-Adams was recently remodeled under the demanding eye of Rose Narva, who has overseen the restoration and remodeling of three hotels on 16th. Now the Hay-Adams has a bright and sunny south dining room overlooking the park. But traditionalists prefer its great old dark-paneled restaurant, suitable for ordering sauerbraten and apfel ku chen.

Two large houses, designed by Hornblower and Marshall and built in 1886 and 1887, stood opposite each other at 16th and I, until they were torn down in the mid-'60s for the Motion Picture Institute and a church.

The Third Church of Christ, Scientist and the Christian Science Monitor Building were built in 1972. The church -- unlike nearby St. John's Episcopal, which welcomes passersby with an inviting portico -- seems to want to keep itself to itself, in the manner of its times and role as an urban sculpture. Architect I.M. Pei took as his text, "A Mighty Fortress Is Our God" in designing this one. Only the bells that protrude from the massive concrete structure are open to the street. To see the inside, go just before services at noon and 8 on Wednesdays, and at 11 Sundays. (I.M. Pei and Partners were architects of the National Gallery of Art's East Building, also more a sculpture than a building.)

The Sheraton-Carlton Hotel, at 16th and K, is worth at least a drink at the bar to admire its magnificent gold-leaf vaulted and embossed ceiling. The Carlton, as oldtimers call it, was designed in 1925 by Mesrobian, a busy architect and builder who obviously knew central European hotels well, and Wardman, who built all the great yellow-brick houses up the street (not to mention the Sheraton-Washington, a wing of which still carries his name). You expect to find feather comforters in every guest room.

The Soviet Embassy, the great beaux arts embassy at 1125 16th, looks as though it belongs to an ancien regime of the czars rather than the communists. If you go back far enough in Washington, you might call it the Pullman mansion, after Harriet Sanger Pullman. She was the widow of George Pullman, who organized the Pullman Palace Car Co.

About 1910, that dowager commissioned architect Nathan Corwith Wyeth to design the house for her daughter and son-in-law, Frank O. Lowden, an Illinois congressman, but neither she nor they ever lived in the house. It was sold to the Imperial Russian government in November 1913.

The story (hotly disputed) goes that the last imperial ambassador, George Bakhmeteff, left for his Paris exile with many of its antique furnishings. He married Marie Beale, daughter of Gen. Edward Beale of Decatur House and sister of Evalyn Walsh McLean's mother-in-law, Emily Beale (Mrs. John R.) McLean. The Soviet government took possession of the house in 1933 and has rejoiced in it ever since.

Wyeth, a notable Washington architect, had designed the Oval Office in 1909. For the Pullman house, he borrowed bits from here and there as he'd been taught at the Ecole des Beaux Arts in Paris. The embassy's one of our grandest examples of Edwardian ornate (or Taftian taffy). The tall Second Empire roof and windows command awe.

Although the mansion's rather ornate for a workers' republic, the Soviet government has been meticulous in keeping the mansion up to the gold standard. They even brought a gold-leaf expert from the Soviet Union to regild this lily.

The piano nobile (the main floor, on the second story) is divided by the sweeping stair. The wood-paneled banquet hall on the east is often set up for buffets that star copious caviar. The gold-leafed west salon, festooned with plasterwork, mirrors its chandeliers until you think there must be a million of them. The salon was unaccustomedly vodkaless on the departure of Ambassador Anatoliy Fedorovich Dobrynin because of a new purge of the strong drink at home.

A small reception room on the south and a stair to the ambassador's private quarters on the north complete the square. The Soviets have been building an embassy complex on Mount Alba, but may not be allowed to move in until the difficulties with our new Moscow embassy have been solved. Anyway, the word is that the Soviet ambassador, who knows a good thing when he has it, plans to keep the house as his residence.

Glasnost or not, the embassy's not open to the public, and the handsome shutters are usually tightly closed lest secrets peek out. Protesters of various persuasions frequently parade nearby. And a street sign proclaims this block of 16th Street as Andrei Sakharov Plaza, though you'll find no evidence of Congress' 1984 tribute to the Soviet dissident on the embassy's letterhead.

The National Geographic Society's Gardiner Greene Hubbard Memorial was built 1901-1904 on the southwest corner of 16th and M. The building honors the Society's founding president (1888). Joseph Coerten Hornblower and James Rush Marshall (whose two houses at 16th and I were torn down) designed the building.

Originally, Hubbard Memorial was primarily a lecture hall. On the ground floor were marvelously paneled offices, sometimes used today for the luncheons for which the National Geographic has a tasteful reputation. The building represents the best instincts of the period. The excesses of the Benjamin Harrison and Grover Cleveland era were rejected in favor of a stripped-down yet graceful style, a suitable setting for explorers and writers. The long windows on the second, or piano nobile floor, have arched eyebrows.

Arthur B. Heaton was the architect for the first addition in 1914, as well as the center and south wings in 1931; they're chaste Classical Revival, less adventuresome and more self-important than the earlier one. Heaton let himself go opulently in the foyer, the only part open to the public.

The red-marble columns stand guard around a great marble western hemisphere, the magazine's old logo. Among the marbles used in the entry are Italian Betticino, Belgian black, yellow Mankato, Tennessee pink, French green and Spanish Rojo Alicante, as well as North Carolina pink and gray granite and Indiana limestone.

To see more, you have to call Cynthia B. Lew, 857-7686.

The public is welcome to the National Geographic's Explorers Hall, in its building designed by Edward Durrell Stone in 1964, a block down M at 17th. Explorer's Hall is open from 9 to 7 weekdays, to 5 Saturdays and noon to 5 Sundays.

The Jefferson Hotel, at 16th and M, benefits from having been designed in 1923 by Jules Henri de Sibour (1872-1938). Legend says he descended from the lost Dauphin, the son of the deposed and decapitated Louis XVI of France.

This charming small hotel is owned by lawyer Edward Bennett Williams and presided over by the legendary Rose Narva, who runs the place as though it were her own chateau. The Jefferson's the best place in town to be stuck in the elevator. Indeed, once when a new elevator broke down with a carload of dinner guests, Narva not only produced an antique brass-bound rescue ladder but laid a delicate cashmere shawl over the top so no dress would be sullied. A waiter in black tie presented the rescued with drinks on a silver tray.

Its restaurant is full of nooks and crannies, the better for assignations and conspiracies, making it a favorite of politicians. The white-chocolate mousse isn't bad either.

De Sibour designed four great mansions, which eventually became the French ambassador's residence, the Peruvian Chancery, the Canadian chancery, and the Embassy of Luxembourg. He also designed the more sedate University Club at 1135 16th.

The de Sibour townhouse at 1128 16th, beautifully detailed stone and brick, seems almost austere until you notice the amusing peaked windows on the first floor. It's now offices, owned by the 1128 Sixteenth Street Corporation.

The exuberant, almost art nouveau house at 1218 16th was built in 1907 for a Dr. A.O. Bliss. It's now law offices. You'd expect to find its facade in Paris or Brussels, where the fin-de-sie`cle style was rampant. Its cheerful frivolity -- mansard roof, window glass set in whiplash frames -- in this staid Georgian city is rather like finding a chocolate-dipped kirsch cherry in a box of caramels.

Scott Circle, where meet the two great rivals, 16th Street and Massachusetts Avenue, is worth a careful walkabout (careful may not be a strong enough word, considering the traffic). Scott Circle is a circle only by courtesy. Actually, it's an oval with two extra parts.

On the eastern "island," Dr. Samuel Hahnemann, the great guru of homeopathy, broods eternally over his 1789 Leipzig philosophy: Similia Similibus Curentur ("Likes are cured by likes"). He ponders in the middle of an exedra, "a large outdoor nearly semicircular seat with a solid back," as Webster's says. The 1900 bench serves well to examine the bronze relief panels illustrating his work. Charles Henry Niehaus was the sculptor, Julius F. Harden the architect.

On the western "island" is a traditional bronze statue of Daniel Webster by Gaetano Trentanove, which was also mounted in 1900. The two inset high-relief sculpture panels are intricately modeled scenes showing the greatest hits of the famous orator. John C. Calhoun, Robert Young Hayne and almost 100 other figures of antebellum politics convene to hear the great man in one panel. Stilson Hutchins, founder of The Washington Post and, like Webster, a New Hampshire native, donated the statue.

Ah yes, there is a Scott on Scott Circle. Lt. Gen. Winfield Scott himself, in 1874, cast in bronze, mare and all, from cannon captured in the Mexican War. The pedestal was carved out of a 150-ton block of granite. Henry Kirke Brown was the sculptor. The Whigs nominated Scott for president in 1852, but he lost to Franklin Pierce. He died in 1866 at West Point.

The huge red-brick house at 1401 16th was built in 1888 by Samuel and Charles Edmonston, great contractors of the period. They borrowed inspiration from H.H. Richardson, whose Hay-Adams house on Lafayette Square the company also had built. The vast entrance, designed for the corpulent Richardson, leads into a lavishly carved wood-paneled vestibule. The staircase repeats its open rectangle up three floors to a stained-glass skylight.

Architects Henry Grant Ingersoll and Glenn Chen Fong won a citation for their restoration of the house, which had been used as a dental hospital. Columnist Jack Anderson and lawyers William Ingersoll and Stuart Bloch bought the house in 1974. It has had other notable tenants: Vice President James S. Sherman, who died in office, lived there from 1911 to 1912; Sen. Russell A. Alger of Michigan had it earlier.

For a gaudy interval it was an opulent red-velvet bordello, for which its William McKinley-period style was ideally suited. The house still has gaslight-era crystal chandeliers. The ceiling in Bloch's office, the original dining room, is divided into octagonals by the carved wood molding.

Charles Marlatt's house at 1521 16th, not Mayor Barry's, is the most bugged dwelling in Washington. L. Norris designed the house in 1908 for Marlatt, chief of the entomology division of the Department of Agriculture, who liked to bring his work home with him. The paneled first floor is full of bugs, all neatly carved into the woodwork in high Arts and Crafts Movement style. This innovative style of the turn of the century is more often found in the Midwest or West (architects Frank Lloyd Wright, Greene & Greene), than in our more staid East.

Soviet military attache's once had their offices in the house,(before they moved to the grander, but less fun, Lothrop mansion at Connecticut and Florida, designed by the aforementioned Hornblower and Marshall). The charming bughouse, still used for offices, retires gracefully in a corner of its lot, making room for a curved driveway.

The Church of the Holy City, Swedenborgian at 1611 16th, is made of Bedford limestone, in the manner of the 13th- and 14th-century Decorated Gothic style. Crane your neck to see the tower pinnacles, crockets (edge ornamentation) and crenellations (battlements). Fearsome beasties leer down at you from the gables. In the attached Lady Chapel, a disguised curving staircase leads to rooms now used by the St. Hilda of Whitby Anglican Catholic Church. Pelz and Carlisle were listed as the architects in 1894 with Warren and Smith responsible for the staircase and classroom addition in 1912. But the principal design credit goes to Herbert Langford Warren, a founder of the Harvard school of architecture and a Swedenborgian. Sunday services, from 11 to noon, resume in mid-September; discussion sessions are held from 9:30 to 10:45.

The Denman-Werlich house at 1623 16th was built for Hampton B. Denman, mayor of Leavenworth, Kansas, who came to Washington in the 1870s. He must have brought a pile of money with him, because he commissioned Fuller and Wheeler of Albany to build him a fine house situated in the middle of five lots in 1886.

The architects were obviously heavily influenced by Richardson Romanesque style, from whence came the swallow-you-up entrance and the romantic tower. Its great chimney is surely one of the fanciest in town. The basement and first floor are faced with sandstone, with brick on the upper floors. Denman left all his money to the Georgetown and George Washington University law schools and Catholic charities, but his family sued and won. They sold the house to Eleanora O'Donnell Hinckley, who added the conservatory, designed by architect Frank H. Jackson in 1906.

Her daughter Gladys married McCeney Werlich, and lived in the house from 1936 until, at age 84, she was murdered on the street by young thugs. The house is now used as offices.

The Toutorsky Residence at 1720 16th was built in 1894 for Supreme Court Justice Henry B. Brown, to a wonderful design by William Henry Miller. The Fine Arts Commission says Miller combined elements of Arts and Crafts, Queen Anne and Romanesque styles in his design. To that you have to add a strong dollop of sheer mad fun. The house arouses covetousness in all right-thinking people.

Brown lived there until 1913. In 1947 Russian pianist and music professor Basil P. Toutorsky and his wife, Maria Ignacia Howard Toutorsky, a Spanish teacher, turned the house into a music academy. The Toutorskys have made it a private schatzkammer of amazing antiques and instruments: Liszt's Bechstein piano, oriental rugs, porcelain swans . . .

The Scottish Rite Temple at 1733 16th was inspired by one of the seven wonders of the world, the Hellenistic temple-tomb of King Mausolus at Halicarnassus. And surely it is one of the wonders of Washington today. It's the mother temple of the Scottish Rite Freemasonry as well as the headquarters of the Supreme Council, 33rd degree.

John Russell Pope, (1874-1937) its architect, was the monument maker of Washington. From his drafting board came the National Archives, the National Gallery of Art, the Jefferson Memorial, the Textile Museum and seven houses, including the two atop Meridian Hill. He also designed the Baltimore Museum of Art and the British Museum's Duveen wing housing the Parthenon sculptures, to skip lightly over his career.

The temple cornerstone was laid in 1911, in a ceremony employing the Bible, trowel and candlesticks of Potomac Lodge No. 5, used by George Washington to lay the cornerstone of the Capitol.

Behind the huge columns are an elaborate gold inscription and symbolic decorations. The entryway's guarded by two sphinxes, lionesses with the heads of women. On the right is Wisdom, on the left, Power; each is about seven feet tall and five feet wide, sculpted of limestone by Adolph Alexander.

The Temple Room, comprising the entire upper floor, is the stage for the biennial ceremonies of the Supreme Council, including the conferring of the 33rd degree. The building also has an executive chamber, banquet hall and a museum and library, all elaborately and ceremonially decorated on an awesome scale.

You can join an hour tour of the building any day between 9 and 2. Then take a break. Rest up to do Meridian Hill and Lafayette Park on other days.

A word of advice: admire the houses only from the sidewalk or street (come back for quick glimpses at lighting-up time, before the shades are drawn). From Scott Circle to Florida, none is open to the public.

On Saturday or Sunday, depending on the creed, stay for the services and admire the sanctuaries or chapels. Not many of the churches are open other days.

Start your trip at the Commission of Fine Arts, 708 Jackson Place NW, to buy its scholarly and gossipy Sixteenth Street Architecture, Volume 1, by Sue Kohler and Jeffrey R. Carson. Volume 2 will be out next year. Pause at the National Trust for Historic Preservation bookshop and buy James Goode's entertaining and comprehensive The Outdoor Sculpture of Washington, D.C., and the American Institute of Architects' indispensable A Guide to the Architecture of Washington D.C. by Warren J. Cox, Hugh Newell Jacobsen, Francis D. Lethbridge and David R. Rosenthal.

Washington Post Staff Writer Sarah Booth Conroy has lived on Sixteenth Street for twenty years.