OT long ago, South Norwalk, Conn., barely knew it had a riverfront. Its once-thriving blocks on the narrow Norwalk River had become mired in decay, and few locals, let alone visitors, cared to venture there. In the last decade, the area has been transformed. Today South Norwalk, known by its suburban-hip moniker of SoNo, is a charming historic district offering, in a compact day trip, everything from restored architecture to martinis with a view.

SoNo's tree-lined streets hold an eclectic mix of lively boutiques, restaurants and museums, most of them housed in graciously preserved 19th-century buildings with majestic brick facades. The gleaming river and Long Island Sound, which it meets in Norwalk, are more than a backdrop. Instead, the water is celebrated here as an integral neighbor: at beachfront parks, at SoNo's annual oyster festival and, most delightfully, at the Maritime Aquarium.

Built to anchor SoNo in 1988, the aquarium is bursting with seaworthy delights: impish river otters somersaulting behind a wall of glass, goofily bucktoothed sand tiger sharks constantly on the prowl and jellyfish floating like round, diaphanous pillows in a cylindrical floor-to-ceiling tank. There's also an Imax theater showing thrilling films that take you below the sea. "Fish rock!" Vicki Sawyer, a resident aquarist declared one day last month as she cooed to her finned friends through the aquarium's glass.

In October and November, the aquarium runs foliage cruises on the sound, led by marine biologists who point out the creatures there.

The aquarium may or may not dull your taste for seafood. Either way, you're spoiled for choice along nearby Washington Street, on SoNo's overstuffed block. Restaurants from Japanese to nouveau-fusion are decked out with bright, slick interiors, one more inviting than the next. The funky SoNo Caffeine lounge has snacks and salads in a sultry setting. On North Main Street, SoNo's second but less-gussied-up strip, there's more good fare at places like Habana, serving Cuban food, and Barcelona Restaurant and Wine Bar.

Whatever the choice, you can walk it off afterward on the brick sidewalks, where oxford-and-khaki-wearing locals jabber into cellphones and pristine storefronts beckon you to shop for 400-thread-count linens, oil paintings, Giraudon shoes and black pottery from Mata Ortiz, Mexico. Or stroll along the river on the quiet path behind the aquarium.

If you've come by car, it's worth driving across the river later to the public Calf Pasture Beach City Park, which offers sweeping views of the sound and the Norwalk Islands. But in SoNo, history still awaits.

Among the displays in the small Norwalk Museum, in a columned building that used to serve as City Hall, are local redware pottery, about 30 Raggedy Ann dolls (an artist named Johnny Gruelle created Raggedy Ann while living in Norwalk in 1917), and the largest collection of works by residents of the early-1900's Silvermine art colony, now the Silvermine Guild Arts Center, in nearby New Canaan.

You won't need much time for the tiny elevated SoNo Switch Tower Museum at the end of Washington Street, but it's fun to stand above the Amtrak and Metro-North lines and pull the stiff wooden levers that controlled the tracks from 1896 till 1984.

Historic Norwalk's pièce de résistance is the grand old Lockwood-Mathews Mansion Museum, a brisk 10-minute walk from SoNo. This partly restored Victorian behemoth, built with Wall Street wealth in the mid-1860's, boasts original marble floors, carved walnut mantels and a rare 19th-century music box collection. The lavish rotunda appeared prominently in the recent remake of "The Stepford Wives." Hollywood's use of the space is an apt representation of the Norwalk that has given birth to SoNo — a place where the past is the platform for reinvention.

Easily Accessible, by Road or Rail

TO get to SoNo from Interstate 95, take Exit 14 from the south and Exit 15 from the north. Then head south on West Avenue until it turns into North Main Street.

From the Metro-North South Norwalk station, walk east on Monroe Street and then north on South Main Street. When South Main Street becomes North Main, Washington Street will be on your right.