Near the Presidio's Lombard Gate, a building with a familiar face but bigger shoulders reveals itself. It's not the graceless ten-story concrete bulk that was the Letterman Army Medical Center, with its sprawling parking lot; it's part of George Lucas's brand-new Letterman Digital Arts Center. Recall that after the federal government turned the Presidio over to the National Park Service in the midnineties, it came with the mandate that the park pay its own way by 2013. Hence the big commercial tenant—and one with a high-profile media empire in tow. This now-grassy 23 acres accommodates Lucasfilm headquarters, which includes the game division LucasArts and the digital effects powerhouse Industrial Light & Magic.

Just as when he's making a film, Lucas's architectural custom is to lie low. In Marin County, his Skywalker Ranch and Big Rock complexes look more like wine estates as you whiz past them on Lucas Valley Road; ILM's former headquarters are in a nondescript building in San Rafael. The buildings are as much a manifestation of Lucas's notorious culture of secrecy as the phony movie titles that his crews use to elude fans during production shoots. Of the buildings on Lucas's new campus, only the ground-level café and a proposed 8,000-square-foot restaurant will be open to the public. But all that greenery—on 17 of the 23 acres—is available to everyone. This means that for all the globally blockbusting media that built the Lucas empire—the Star Wars and Indiana Jones films, the video games, the THX sound and effects production units—the Letterman center is arguably the most communal overture in Lucas's history.

After the initial plan was deemed too corporate for the site (and as having too little public access), the Lucas team looked to the Presidio's utilitarian yet distinguishing military architecture.   To head his design team, Lucas picked Kevin Hart of San Francisco's Gensler Architects, who designed Lucas's villalike Big Rock campus and, more recently, the Jewish Community Center in the Richmond district, a prime example of a big new structure trying to conform to its surroundings. The lack of innovation is all to the good here.

Outwardly at least, the Letterman center adapts the simplicity of much of the post's architecture of the late 19th and early 20th centuries. Numerous neocolonial, Mission revival, and Georgian revival structures dot the old Army base, but the features that most people identify with the Presidio are the unadorned brick and milky clapboard facades, the red roofs, shallow eaves, and small-paned windows. The center has retained these elements, and not just to win the lease.

Unless you're an employee or a select visitor, though, you won't be enjoying the fitness center, day-care facilities, and three state-of-the-art screening theaters. (The sublease tenants can use the first two.) Most of us will experience the Letterman campus by way of the verdant Great Meadow, created by the venerable but unflagging landscape architect Lawrence Halprin, who designed the FDR Memorial in Washington, DC, the Levi's Plaza fountains and park below Telegraph Hill, and the newly refurbished Stern Grove, among many other projects in his long career. Lucas didn't turn to Halprin solely because he's a local legend, though. Halprin plans his environments the way Lucas does his films: down to the last detail, even if it is not immediately perceptible. Halprin selected the stones and all the flora here, which include blue oat and autumn moor grasses, Japanese maple, several kinds of gum trees and lilies, and other fruiting and flowering plants.

Halprin's projects are a concatenation of elements to engage both sight and hearing; his hallmark water components tend to fuse or smooth out the arrangements. At the Letterman center, the water originates on one of two artificial promontories positioned along "view corridors," each of which aligns with Bernard Maybeck's 1915 Palace of Fine Arts. From these "stony belvederes" (the archaic, pastoral names of Halprin's features reflect his romantic streak), a man-made creek runs down to a small lagoon, following a conceptual path that would flow all the way to the Palace's pond were Gorgas Avenue not in the way. Halprin himself designed the meadow's green lamps, benches, and a small iron pavilion with restrained geometric and floral detailing that subtly evokes the Victorian age. As for the modern day, you won't find any tacky design references to the Star Wars franchise or any Lucas logos or signs. The only nod to the empire is a statue of wizened little Yoda presiding over a fountain right outside the visitor's entrance.

But even with all these thoughtful, subtle features and worthy good-neighbor overtures throughout the plaza, the proportion can still feel off. You and your sweetie may be enjoying the greenery, the views, the way the Palace of Fine Arts burnishes and glows at dusk, but don't look back, or you'll see the crouching complex behind you. Even when you're standing amid the hillocky landscape on the small stone bridge that spans the creek, your mood can snag on the feeling that institutional buildings loom. Though visually consistent with the setting and far more welcoming than the old hospital, the new structures are still huge—865,000 square feet in total, down from the original 900,000. The buildings, at present simply tagged A through D, are generally divided into two wings (Building A has three) connected by glassy pedestrian bridges. This device serves to offset the aggregate mass of the buildings, but it multiplies the surface area and creates a density of rooflines.

The buildings are meant to fit quietly into the park even as one of the most powerful computing networks in the entertainment industry lies behind their homey brick and "Presidio white" walls. The landscape offsets the scale of the buildings, but a subtle tension remains: in proportion, the Lucas buildings relate to the surrounding and stylistically similar Presidio buildings as Monopoly hotels do to the little game-piece houses.

The Letterman Digital Arts Center retains a discreet but palpable division of public and private, and the success of this major endeavor will rest on how many locals and tourists frequent the plaza. I'm betting they will come, and often. Bucking a trend so pervasive it seems almost miraculous—to add more public green space to this dense and costly city—makes this a valuable and surely long-lived achievement. Let's be grateful for the silence of the tenant. Ironically, until Star Wars: Episode III departs from local theaters, this will be one of the few publicly accessible commercial spaces in the Bay Area where one can go without being badgered into a chain store by a six-foot-high cardboard Sith.