Getting around Washington's circles and squares can be a daunting experience for the uninitiated motorist. Those circles and squares are nonetheless essential elements that define Pierre L'Enfant's plan for the District as much as the broad avenues and angled streets that radiate from the center of the federal city.

"The L'Enfant Plan laid the foundation for modern Washington," the National Capital Planning Commission recalled in "Extending the Legacy," the long-range planning guide developed by the agency three years ago.

Yet in the decades that followed the adoption of L'Enfant's 1791 plan, the NCPC continued, "many of its bold ideas were ignored or subverted."

Nowhere is that more evident than in the area around Mount Vernon Square, currently the focus of development speculation, due primarily to construction of the District's new convention center just north of the square.

From L'Enfant's conceptualization of the original federal city to the present, planning policy for the Mount Vernon Triangle favored a mixture of residential and commercial uses, according to the Committee of 100 on the Federal City.

Obviously that planning policy would be subverted if District officials were to approve a highly publicized proposal to cram a major league baseball park into the triangular-shaped area east of Mount Vernon Square.

Still, the idea of building a baseball stadium in that area isn't nearly as bizarre as an aborted plan to build a massive 7,000-vehicle underground garage, or intermodal center as it was called, in the same area.

While both of those proposals may seem odd, they are in fact part of the familiar pattern of ad hoc development that has been allowed to shape the city's old downtown area in a decades-long planning vacuum. The new convention center is Exhibit A. It's the equivalent of a circus tent being squeezed into a back yard.

We could see more subversion of planning policy in the Mount Vernon Square area unless city officials adopt a concept plan recently developed by the Committee of 100, the District's oldest citizen planning and advocacy organization.

The Committee of 100's concept plan is really the first proposal to capture the essence of the so-called "living downtown," providing for a mix of commerce and housing in the context of the L'Enfant Plan.

"Longstanding planning policy calls for the [Mount Vernon Triangle] to be a vibrant, in-town, mixed-use neighborhood--where residents and workers mingle and the development pattern transitions between the intense downtown [area] and the less dense townhouse fabric of historic Shaw," the Committee of 100 noted in explaining the rationale for developing the concept plan.

The concept plan translates the vision of an extraordinary model of revitalization and economic development in the triangular-shaped 18-block area, framed by Seventh Street and New York, Massachusetts and New Jersey avenues NW. There is no better location for achieving the kind of transition and uses envisioned by the committee.

Based on its study of land records, development potential and demand, the committee estimates that redevelopment of the area in question would produce more than 4 million square feet of residential space, including 3,240 new housing units, and 4 million square feet of commercial space. The mix of housing, offices, hotels and retail space would generate an estimated 13,000 new jobs and $46 million in net new taxes for the District.

"This concept plan is doable without massive investments in blockbuster projects that are neither desirable or necessary," the Committee of 100 asserted in a draft of the plan that is being circulated among city officials and community organizations.

There currently is a mixture of housing and businesses, most of them in low-rise structures, scattered throughout the Mount Vernon Triangle. Even so, about 60 percent of the land would be redeveloped, according to Joseph Bender, one of the concept plan's principal authors and a principal with Potomac Land Associates Inc.

The committee's research shows, however, that the District already owns more than 45 percent of the land area that would be developed under the plan. With that kind of leverage, the city should have little difficulty in making the Committee of 100's concept plan a reality.

In presenting the draft of the concept plan, the Committee of 100 noted pointedly that the city's job is to help create an environment in which investors may take advantage of opportunities as the market emerges.

That said, District officials would be terribly remiss if they were to conduct business as usual, reject the committee's concept plan and forgo yet another opportunity to create a thriving commercial and residential center in the city's East End.