Fly into National Airport from the northwest, along the Potomac River, while sitting on the left side of the airplane. On a clear spring day, you will experience one of the most dramatic, lump-in-the-throat approaches to the nation's first planned city.

Acoustically unfortunate for those below the flight path, it is a revealing and inspiring arrival for flyers. From this vantage point, the eye can quickly comprehend the unique shape of the capital city. When the airplane banks to the left at a thousand feet, you can grasp Washington's compositional rationale in overview.

Approaching Cabin John, you see an overwhelmingly verdant landscape, a tapestry of trees punctuated by rooftops and office or apartment buildings jutting up inside, outside and around the Beltway. The pattern of residential neighborhoods separated by fingers of wooded parkland becomes evident. The George Washington Parkway and the historic C&O Canal flanking the Potomac lie below.

Moving downriver, you spot the Washington National Cathedral sitting high above Cleveland Park and the city's northwest quadrant. It serves as a Gothic-styled architectural and spiritual landmark. Far to the east of the cathedral rises the Shrine of the Immaculate Conception at Catholic University. From many points in the District, these two churches rival the Capitol as landmark buildings. In fact, when approaching the city by car from the northeast along New York Avenue, you see all three of these buildings, along with the Washington Monument.

As the plane nears Georgetown, the northern and western sections of downtown come into view. On the right in Virginia, the pilot can see suburban McLean and Arlington criss-crossed by a network of roads that defy navigational comprehension by any nonresident, while Rosslyn rises threateningly ahead.

The rectangular pattern of streets and housing in Georgetown is clearly visible among dense canopies of leaves. In new Georgetown, between the river and M Street, the dominant material is brick and the dominant color red. In the minority are grays, browns and beiges with which brick and wood buildings have been painted.

Red brick prevails in the West End as well. But in Foggy Bottom and the business sections north and south of K Street, red brick, though back in style, is still subordinate to the variety of modernist materials -- glass, stone, metals, pre-cast concrete -- which characterized nonregional, commercially inspired architecture of the last 30 years.

The behemoths of Watergate and the Kennedy Center loom over the Potomac River and help suggest the transition from the red brick to white marble sectors of Washington. Meanwhile, the pilot, having avoided Rosslyn, can see Arlington National Cemetery, the Pentagon and a mind-boggling tangle of highways that somehow resolve themselves as they converge on the Potomac River bridges.

Just before landing, L'Enfant's Washington comes fully into view. The reds, browns and beiges have given way to the white and gray and green of Washington's governmental core. The me'lange of materials to the north and west has yielded to the marble, granite and limestone of monumental downtown.

That it all can be taken in and recognized so quickly is a special attribute of this city. There is a disarming simplicity and clarity to the scheme. The organization of this symbolic landscape is not obscured, even at ground level.

The long east-west axis between the Capitol and the Lincoln Memorial is reinforced by the elements of the Mall -- its parallel rows of trees, graveled pathways, drives, flanking museums, the Washington Monument and the Reflecting Pool. The romantic, curvilinear gardens north of the Reflecting Pool intensify awareness of this axial relationship. If you look beyond the Capitol, you see RFK Stadium at the terminus of East Capitol Street where the axis intercepts the Anacostia River.

Opposing this axis is the shorter north-south axis established by the White House and Lafayette Park, the South Lawn and Ellipse, the slightly-off-axis obelisk (which flags the crossing of the axes) and the Jefferson Memorial at the edge of the Tidal Basin. Especially wonderful is the way in which this irregularly shaped adjunct to the river, bordered by blossoming cherry trees, penetrates into the organized geometry of the core, as if it were assertively biting off a piece of the Mall to create East Potomac Park.

Further contemplation reveals that these perceivable relationships are created by broad expanses of shaped lawns and discernible geometric figures inscribed on the ground, which interact with the free-standing buildings and monuments marking the axes. Other buildings lining Constitution and Independence avenues and 15th and 17th streets help to define the edges of these great spaces. You know that it has been designed, that there's a logic behind it all.

You trace the diagonal avenues -- Virginia, Pennsylvania, Connecticut, New York, Vermont, Massachusetts, Maryland -- lined by buildings and slicing through the grid of streets just as L'Enfant had planned. Squares, circles, plazas and parks cloaked in green are everywhere. Looking north, you can follow the marvelous intrusion that Rock Creek Park makes upon the city as it twists and undulates its way toward Maryland.

With the plane losing altitude, you see the city increasingly as facades in elevation and less as roofs in plan. Devoid of high-rise buildings, it is a "mat" city woven sometimes tightly and sometimes loosely. This characteristic seems exemplified by the tile-roofed Federal Triangle wedged between the Mall and Pennsylvania Avenue. Except for the happily preserved Old Post Office and National Archives, the buildings of the Federal Triangle look as if they were meticulously cut out from a monolithic, horizontal slab of material that then was painted red on top.

Washington clung to its building height tradition in deference to the memorable silhouettes of its symbolic buildings and monuments. Thus it differentiated itself sharply from other American cities where skyscrapers have engulfed urban cores and themselves have become the new monuments and landmarks.

So, in sum, what do we have in Washington? Physically and perceptually, it's a low city, a green and spacious city, a river-fronting city, a city with a center whose form is recognizable and measurable. Like a great house with a great room and a great hearth, Washington has its grand, central place around which people can work, conduct business, dwell and recreate. Even suburbanites who rarely venture downtown subconsciously sense its distant presence and availability. You only have to visit cities such as Los Angeles, Houston or New York to understand what we have and they do not.

But beyond function and form, there is conceptual and symbolic significance. Not only does the heart of Washington offer a sense of place, but it also represents ideas and events. We see its form, but intellectually and emotionally, we feel something more.

We see monuments to Lincoln and Jefferson and Washington, but we also think about the Declaration of Independence, the Constitution and the Bill of Rights, the Emancipation Proclamation, liberty, democracy, war and peace. Up the avenues in business or residential districts, down-the-avenue sighting of the Capitol dome or Washington Monument may pull thoughts momentarily away from personal affairs, an arresting visual reminder of where you are and what it might mean.

L'Enfant's Washington is the nation's village green, its town square, a place to remember the past, celebrate the present and plan the future.

NEXT: Buildings -- Parts That Make the Whole