As of noon today, the 50,000 residents of Reston will have their very own downtown.

Or a portion of a downtown. The first phase of Reston Town Center has just been completed, and the 20-acre development will be dedicated in a ceremony at noon today. The finished part includes a central plaza, two 11-story, beige brick office buildings, a 14-story hotel, 60 shops and restaurants, an 11-screen movie theater and smooth new roads lined with wide, brick sidewalks.

The rest of the 84-acre town center that developers Reston Town Center Associates and Himmel & Co. promise will be the hub of the 26-year-old planned community is expected to be phased in during the next 10 years.

For urban planners, the $350 million first phase is a showcase of suburban design concepts that has taken years to research and plan. For many Reston residents, the town center promises to be an alternative to Tysons Corner and other shopping, eating and entertainment areas in the metropolitan area.

"We're all interested in how it develops. It's like looking at a new baby," said Martha Green, a member of the board of directors of the Reston Association and, like other Reston residents, often shops at malls 15 minutes away. The Reston Association, a panel that represents the property owners and residents of Reston.

The dedication ceremony will begin with the unveiling of a statue of Mercury, the Greco-Roman god of commerce, atop a marble fountain in the heart of the town center's central plaza. Robert E. Simons, the founder of the community of Reston, and Martha V. Pennino, who represents the community on the Fairfax County Board of Supervisors, will then be honored for their roles in developing the project.

A private lunch for 400 invitees, including civic and business people involved with the project, will follow. When the town center is completed, it will include 5 million square feet of office space, 400,000 square feet of retail space and about 1,600 housing units.

Although the town center has been in the making for years, some issues remain unresolved. For instance, it is still undecided whether future inhabitants of the residential portion of the town center will be subject to the same rules as other community homeowners.

Community leaders believe that town center residents should be required to get permission from the Reston Design and Review Board before they make architectural changes to their homes, just as other Reston residents must do.

But the key to the town center's success ultimately rests with people's tastes.

"We've done everything we possibly can in terms of research, in terms of what it promises and what we can deliver, in terms of street experience, in terms of parking . . . but the public will tell us whether we've made the right decision," said John Tyers, marketing director for Reston Town Center Associates.

"The only drawback may be . . . prices. If the prices are too high, people will go somewhere else," said Reston Association board member Dan McGuire, who described himself as a conscientious shopper. On the other hand, he said, "if merchants do not put price tags out of reach of people, they've got a tremendous opportunity there."