Subway: Take the N or R to Fifth Avenue.

Finish: 91st Street and Fifth Avenue.

Time: Approximately 3 hours.

Best Time: Weekday afternoons, when museums and restaurants are open but not as crowded as on Saturdays.

Worst Time: Sundays, when most stores and galleries are closed and the streets seem deserted.

The Upper East Side

Over a century ago, society watchers predicted that the wealthy and fashionable would settle permanently on the avenues bordering Central Park. Time has proven them right. Fifth Avenue north of Grand Army Plaza, which lies at the southeast corner of the park, is officially called Museum Mile. But the magnificent private mansions built here in the first few decades of this century by some of America's wealthiest industrial tycoons also earned it the title of Millionaires' Row. Judging from old photos, it was something to behold.

Today, patrician mansions still stand along the avenue, though others have ceded their coveted real estate to large apartment houses. But the age of imperial living isn't over by any means. Some of the buildings on Fifth Avenue (as well as on Park Ave. and elsewhere on the East Side) contain apartments every bit as palatial and sumptuous as the vanished mansions. Even New Yorkers are surprised to hear of apartments with 20, 30, or even 40 rooms, but they do exist in this neighborhood.

Start your tour where Fifth Avenue and 59th Street meet at:

Now stroll up Fifth Avenue, staying on the park side of the street for the best view of the buildings as you pass. In good weather, bookstalls from The Strand line the sidewalk, full of used volumes at a fraction of the cover price. On the east (right) side of Fifth Avenue, at 61st Street, is:

At the southeast corner of 62nd Street stands the third home of the:

The next block up is 63rd Street. On the east corner you'll see:

Continue northward on Fifth Avenue to 64th Street. Walk just inside Central Park for a look at:

Head back onto Fifth Avenue. Opposite the park at the southeast corner of 64th Street (828 Fifth Ave.) is the former mansion of coal magnate Edward Berwind. This residence dates from 1896 and has been preserved as cooperative apartments.

Head east (away from the park) on 64th Street toward Madison Avenue. This particularly handsome East Side block is lined with architectural extravaganzas. Note in particular:

This opulent beaux arts mansion was built in 1903 for the daughter of Mrs. William B. Astor. The house was designed by Warren and Wetmore, the firm responsible for Grand Central Terminal, and it now houses the Consulate General of India. Also worthy of admiration on this block are nos. 16, 19 (now home to a Wildenstein Gallery open Mon-Fri 10am-5pm), and 20.

At Madison Avenue, turn left and saunter two blocks north to 66th Street. Note the rather fantastic apartment house built in 1900 on the northeast corner of 66th and Madison, and then turn left (west) off Madison onto 66th Street, heading back toward Fifth Avenue.

Among the many notable houses on this block is the magnificent French Renaissance-style house at 5 E. 66th St., with its heavy wooden doors and elegant stonework detail. Built in 1900, it's now home to the Lotos Club, which is dedicated to literature and the fine arts.

Next door, at 3 E. 66th St., is the:

Now double back to Madison Avenue, turn left, and continue north for two more blocks, stopping to browse in any of the boutiques that catch your eye. There's Nicole Miller; La Perla for lovely lingerie; Emanuel Ungaro; Godiva, where you can treat yourself to some coffee and a decadent truffle; and Berk for cashmere. At 68th Street, turn right (east) toward Park Avenue. One of the best houses on this block is:

Walk to the north side of 68th Street to:

The Marquesa de Cuevas bought 680 Park Ave. in 1965, staving off a slated demolition by presenting it to the Americas Society, devoted to educating U.S. citizens about their Western Hemisphere neighbors. The society sponsors public art exhibitions and cultural programs on Latin American and Canadian affairs. The other buildings on this block house the Spanish Institute and the Italian Institute.

Head north on Park Avenue to 69th Street. On the northeast corner stands the:

When you arrive at Lexington Avenue, detour right a few steps to a still-operating branch of Shakespeare and Co. (no. 939), Manhattan's famously literary bookseller whose West Side main branch was put out of business in 1996 when Barnes and Noble strategically built two megastores within walking distance. Double back up Lexington 1 1/2 blocks uptown to 70th Street. Turn left and head back toward Park Avenue along:

This street presents a succession of elegant houses, each more beautiful than the next. Some consider this the finest street in New York. Note in particular no. 125, a post-World War II mansion built for Paul Mellon in a French provincial style.

When you arrive at the Park Avenue end of the block, note the modern building on the northeast corner, which houses the: 

Cross Park Avenue and note 720 Park Ave. on the northwest corner of the intersection. This building is a prime example of the sort of swanky, enormous apartment building that lured former mansion dwellers away from their private houses. The upper stories of buildings like no. 720 often contain apartments with three or four floors and dozens of rooms.

Continue on East 70th Street, crossing Madison, toward Fifth Avenue. Two of the Upper East Side's premier art galleries are along 70th Street.

Next door, at no. 19, is Knoedler and Company (tel. 212/794-0550), a major gallery for established American artists such as Helen Frankenthaler, Adolph Gottlieb, Nancy Graves, Frank Stella, and John Walker.

Nearing Fifth Avenue, you'll pass a lovely courtyard and lily pond, surrounded by stately black iron gates, before reaching the entrance to my favorite New York museum, the:

This collection (tel. 212/288-0700; www.frick.org ) is housed in the 1914 mansion of steel magnate Henry Clay Frick and very evocative of the Gilded Age. The beautiful classic garden overlooking 70th Street was built in 1977. Frick always intended that his art collection be opened to the public after his death. The works are arrayed in rooms, many with Frick's original furnishings, centered around a small, plant-filled atrium with classical styling, a vaulted skylight, and a softly splashing fountain. If you have time for only one museum on this tour, the modestly sized but rich Frick Collection may be your best choice.

Turn right at the corner of Fifth Avenue, passing a beautiful colonnade on the side of the Frick building. Continue two blocks north, and turn right onto 72nd Street, heading toward Madison Avenue. On your left, at no. 9, is the Lycée Français (a French primary and secondary school), housed in an elaborate 1894 building of the late French Renaissance style. At the southeast corner of 72nd Street and Madison is:

Take Madison Avenue up a block to 73rd Street, passing The Sharper Image (no. 900), the catalog store for the gadget-hound in all of us, and Yumi Katsura (no. 907), a boutique showcasing exquisite wedding gowns for the well-to-do bride. Detour to your left on 73rd Street to see:

Retrace your steps back to Madison Avenue and turn left. At the southeast corner of 75th and Madison you'll see the:

Take a Break--In the museum's basement, Sarabeth's at the Whitney (tel. 212/570-3670) is much more than your average museum cafeteria--and more expensive, with main lunch dishes starting at $13.70 and brunches starting at $6.75--but it's delicious!

Leave the museum and continue uptown on Madison Avenue. At 76th Street, you'll pass one of New York's grand old hotels, the Carlyle, which has counted two presidents (Harry Truman and John F. Kennedy) among its famous guests. The west side of Madison Avenue from 76th to 77th streets is lined with a procession of intriguing contemporary art galleries, including the Gagosian Gallery in the penthouse of no. 980 (20th-century artists, including Frank Stella, Richard Serra, Andy Warhol, Mark di Suervo, Chris Burden, and Walter de Maria) and David Findlay at no. 984 (19th- and 20th-century American and European art). On the way to 79th Street, you'll also run into the French gourmet store Fauchon (no. 1000) which boasts a stand-up coffee bar and a menagerie of pastries (all pastry ingredients are French-imported, down to the water).

Turn left when you reach 79th Street and return to Fifth Avenue. The impressive row of buildings includes everything from French château-style structures to neo-Georgian town houses. When you reach the corner of Fifth Avenue, turn left for a look at:

Next door, on the corner of 78th Street, is the classic French-style mansion of tobacco millionaire James B. Duke (as in Duke University). His daughter Doris occupied the house intermittently until 1957, when she donated it to New York University. NYU now operates it as a fine arts institute.

Now turn around and walk north on Fifth Avenue. On your left at 82nd Street is the grand entrance to the:

Continue uptown past 85th Street. The building at 1040 Fifth Avenue was for many years the:

After her first husband's assassination, she moved here so that Caroline could attend school at nearby Sacred Heart. The former first lady adored New York and was often spotted strolling nearby in her beloved Central Park. After her death from cancer in 1994, hundreds of mourners gathered outside this building, many leaving flowers on the sidewalk in her memory.

Continue uptown to:

The intelligent Cornelius III went on to grow his wealth through his love of science--he was a consulting engineer on New York's first subway system--and Grace became the primary New York hostess for almost every visiting monarch and merchant-prince. They moved into a mansion at 640 Fifth Avenue, built in the 1880s by Cornelius III's grandfather William Henry I, which was located down on 51st Street and was the first of a concentration of family houses that at the turn of the 20th century caused Fifth Avenue to be called "Vanderbilt Alley." Despite losing over $8 million in the Great Crash of 1929, the Vanderbilts foolishly maintained their lavish lifestyle throughout the Depression. By the end of the 1930s they were, for Vanderbilts, nearly broke (by which I mean they only had $4 million to spare). They had also become pretty much isolated down around 51st Street, surrounded by ghosts of the Vanderbilt past, lots of noisy traffic, and the new office buildings that had replaced many of the other Millionaire's Row mansions done in by the Depression. Grace and her husband ended up having to sell the 640 Fifth Avenue house, and Cornelius III died in 1942. Grace retreated to this 86th Street address in 1944, but the exile appears, at least from the look of this house, to have been comfortable.

Two blocks further up Fifth Avenue is the unmistakable:

Uptown from the Guggenheim, between 90th and 91st streets, is another major sight, the:

Under the auspices of the Smithsonian Institution, the Cooper-Hewitt (tel. 212/849-8400; www.si.edu/ndm ) is housed in the former Andrew Carnegie mansion. Built in 1901, this Georgianesque palace originally shared the neighborhood with squatters' shanties and roaming pigs. By the time the squatters were gone and the streets were built up with fine houses, Carnegie was dead. His widow lived in the house until 1949.

Across 91st Street from the main entrance to the Cooper-Hewitt is the:

The convent occupies what was once the largest private house ever built in Manhattan. Financier Otto Kahn bought the property from Andrew Carnegie in 1913, and construction of his mansion, which was modeled on the papal chancellery in Rome, was completed in 1918. Other houses on this 91st Street block, notably nos. 7 and 9, are almost as grand.

Take 91st Street east to Madison Avenue and turn right (downtown) if you'd like to end the tour with a pick-me-up.