WITH Philadelphia at the heart of this year's bicentennial celebration of the United States Constitution, the city has become an especially popular spot for visitors. What may surprise and delight them as much as the historical sites - grand as they are - are a host of other institutions, attractions, and amenities that complement the festivities here. Of course, even after many visits, I still get misty-eyed in the Pennsylvania Assembly Room at Independence Hall, where the Declaration of Independence was adopted, or, for that matter, when I run my finger along the crack in the Liberty Bell. (Yes, you're allowed to touch it.)
But I also urge people to see other sites I love just as much - sites where I can promise they won't encounter long lines or tacky souvenirs.
At the top of my list is Fairmount Park, with its lush greenery, 18th-century mansions, and more than 200 works of sculpture. After walking ``the most historic square mile in the country,'' visitors will be happy to learn they can travel 17 miles through the park on Victorian trolleys. For one fare, they can stop at any or all of the eight restored and furnished mansions, the museums, the nation's oldest zoo, and even a Japanese tea house.
When I'm taking friends around the city, we often start at the Philadelphia Museum of Art - sometimes with a walk through the dazzling azalea gardens. The museum, a golden Greco-Roman temple topped with glazed blue tiles, stands right at the entrance to the park. What may be the third most important art collection in the US (after New York's Metropolitan Museum and Washington's National Gallery) is housed inside. Van Gogh's ``Sunflowers,'' Picasso's ``Three Musicians,'' and C'ezanne's ``Bathers'' are among the 100,000 paintings and statues in 200 separate galleries. And, of course, the front steps are famous - Sylvester Stallone trotted up them in his first ``Rocky'' film.
On leaving the museum, visitors may want to take note of the sculptures of three generations of Calders. As you stand in the museum's Grand Hall, Alexander Calder's contemporary mobile ``Ghost'' soars above. If you walk in a straight line toward City Hall, 12 blocks to the east, you'll pass the graceful Swann Memorial Fountain in Logan Circle, sculpted by his father, Alexander Stirling Calder. Then, if you look high atop City Hall, you'll see a colossal statue of William Penn, sculpted by the younger Calder's grandfather, Alexander Milne Calder.
You can spend a full day on a walking tour along the broad Benjamin Franklin Parkway, from the Museum of Art to City Hall. This broad, tree-lined boulevard was designed as America's Champs 'Elys'ees. You'll feel as if you are indeed in Paris if you visit the parkway's little jewel, the Rodin Museum. ``The Thinker'' sits brooding outside the French Renaissance exterior. You enter through Rodin's ``Gates of Hell'' into the most comprehensive collection of his work outside France.
A couple of blocks closer to City Hall, one finds a wonderland of push-button exhibits celebrating every facet of science. The Benjamin Franklin Institute, the oldest science museum in the land, is as modern as tomorrow and fun for all ages. After playing engineer in a 350-ton locomotive or watching robots perform, you can explore the universe in armchair comfort at Fels Planetarium. And if Ben Franklin is your all-time hero, you'll want to visit the institute's Franklin artifacts collection.
Across the street you can stroll into the Academy of Natural Sciences, which will satisfy any dinosaur lover in your family with its new $2.5 million exhibit on the subject. There's also a special ``outside-in'' nature section for children 12 and under.
City Hall itself is open for tours on weekdays, and it ranks as one of the city's most striking architectural achievements. I'll bet you've never seen so many small statues on the fa,cade of one building.
Opposite the north side of City Hall is the oldest Masonic Temple in America, so rich with history and so lush in appointments that it is one of the city's greatest treasures and definitely its best kept secret. Each of its halls - Renaissance, Ionic, Oriental, Corinthian, Gothic, Egyptian, and Norman - rivals Versailles in splendor. Also impressive is the Masonic Library and museum, for the simple reason that a great many of the Founding Fathers were Freemasons, and the memorabilia of that part of their lives is here. Tours are free and are offered on the hour from 10 a.m. to 3 p.m.
Just a block farther north on Broad Street is the Pennsylvania Academy of the Fine Arts, America's oldest museum and art school. The Victorian building - a national historic landmark - is as much a masterpiece as the works that line its rose-hued walls. The wealth of American paintings spanning three centuries includes ``Penn's Treaty With the Indians,'' by Benjamin West, works by Charles Willson Peale (who founded the academy in 1805), Thomas Eakins, Mary Cassatt, Andrew Wyeth, Edward Hopper, and works by current students.
After sampling the city's museums, visitors may want to visit the Reading Terminal Market for lunch and mingle with the Amish who've brought their farm-fresh wares to the city.
The market offers every kind of food imaginable - from Mexican to Thai to American seafood. Another colorful attraction is the outdoor Italian Market, where the produce is just picked, the fish just caught. There's no central eatery here, but most people enjoy browsing and munching as they elbow their way through the vendors' shops.
Philadelphia has its share of elegant boutiques and mammoth department stores, not to mention everything in between. One area that has it all is South Street, full of boutiques, art galleries, antique shops, and ethnic restaurants.