Robert A.M. Stern seems to be everywhere these days. Besides running Yale University's architecture school and producing architecture tomes as fat as two-by-fours, he oversees a large and successful architecture factory in New York City that can turn out buildings in any style you need. It has been doing a big business in Philadelphia.

His firm's substantial output here includes one of his finest buildings ever, the Comcast Tower, a handsome modern obelisk. He's also responsible for a truly awful one, the McNeil Center for Early American Studies on 34th Street. That dull redbrick box is decked out with plasticky-looking white windows and just enough design cues for it to claim Georgian ancestry. It should be a cautionary tale for those hoping to re-create historic styles on a modern budget, particularly in a city that knows the glory of the real thing firsthand.

His firm, Robert A.M. Stern Architects, has nevertheless been called in to manufacture another Georgian-style building for Philadelphia. This time, the client is the American Revolution Center, a group that has been searching nearly a decade for a place to house its collection of important period artifacts. After neighborhood opposition derailed plans for a Stern-designed museum building at the Valley Forge battlefield, then-Gov. Ed Rendell brokered a land swap that gave the group control of the shuttered visitor center at Third and Chestnut Streets. Tuesday's announcement that philanthropist Gerry Lenfest will donate $40 million to the $150 million cause, if the group can raise an equal amount elsewhere, greatly increases the odds that a new history museum will be orbiting Independence Mall.

The Museum of the American Revolution, as it's being called, would be Philadelphia's third new downtown museum in as many years, after the Barnes Foundation and the National Museum of American Jewish History. It suffers from all the weaknesses of Stern's neo-traditionalist design philosophy, and yet it accomplishes something neither predecessor managed to do: It puts the front door in the right place.

Such is the strange state of Philadelphia's civic architecture these days that it is necessary to call out this most basic virtue for applause.

Actually, it's not just the entrance — a tall glass portal on Third Street, facing west — that Stern aces. The museum's entire ground floor is arranged with the aim of engaging the city beyond its walls. South of the museum's entrance, the design calls for a store and cafe with doors opening onto a small plaza where tables could be set up. Stern, and design partner Alexander Lamis, also included windows along Chestnut Street that would offer views into the lobby, and connect the museum to the buildings on the north side of the street.

The overall floor plan is equally smart. The designers locate the important changing-exhibitions gallery and auditorium off the ground-floor lobby, so they will be easily accessible to the casual visitor and tour groups alike. Those interested in the permanent galleries would ascend to the second floor by a sweeping, ceremonial staircase (reminiscent of the one at the National Constitution Center) or elevator. Simple and logical, the plan is an improvement over the cumbersome arrangement at James Polshek's Jewish Museum, where the special exhibitions are a world away in a fourth-floor room, one that doubles as a party space.

The prospect of a new museum at this corner is immensely exciting. It would finally enable the city to rid itself of its remaining Bicentennial fiasco, the tomblike visitor center by Cambridge Seven, which now deadens the eastern edge of the historic area. The active ground floor of Stern's design promises to help reactivate the crucial intersection, and tie the area into the Society Hill and Old City neighborhoods.

What's dismaying about the Museum of the American Revolution is its aesthetics. It is the polar opposite of the thrillingly beautiful Barnes Foundation. While the site plan there is almost willfully disdainful of its urban surroundings, the actual building itself, by Tod Williams and Billie Tsien, demonstrates that it is still possible in this ego-crazed design world to create true works of art that offer a sublime architectural experience. It aspires to timelessness and makes classical references, but without resorting to Stern's remedial architectural language.

Stern has made a career out of criticizing modern architects for attempting such "original" designs as the Barnes. His alternative has been to produce buildings in updated versions of period styles, so that they appear authorless and egoless. In this case, the style is Georgian, the name applied to most architecture built in America in the decades leading up to the Revolution, including Independence Hall and many nearby houses in Society Hill.

Stern's reason for applying this style is that Georgian most reflects the revolutionary moment. He also wanted to relate the three-story structure to the massive U.S. Custom House just behind it on Chestnut Street, designed during the Great Depression in an art deco-inflected version of the Georgian style by Ritter & Shay. Stern sees the museum as the "foothill" to the Custom House's mountainous pile.

The problem is that Stern's period buildings are rarely satisfying in the flesh, as the McNeil Center at the University of Pennsylvania demonstrates. The flat expanses of the facade lack the loving detail and craft that mark real Georgian buildings and give them life. Modern details, like the cheap-looking window frames, intrude on the period fantasy. McNeil is just a step above the false fronts you see at highway restaurants like Outback Steakhouse or Taco Bell.

Could the Museum of the American Revolution be constructed in a way to make its Georgian details feel plausibly like real architecture? Despite a sizable $150 million budget, about the same as the Barnes spent, something tells me it's a long shot. Stern works in broad, generalized strokes. Even some of his most well-funded projects, like his new law school building at Harvard, seem underdone and bland, like an upscale chain hotel.

For me, the telltale sign is the cupola. It's an obvious nod to the one atop Independence Hall. The Independence Visitor Center resorted to the same device in a bid for context. But if you look at the Independence Hall version, you'll see it grows naturally out of the architectural massing, rising up from the outer wings to the gradually telescoping tower. On Stern's museum, the cupola is simply plopped onto a flat roof, as if to say, "Look folks! Revolutionary symbolism." Of course, the museum hopes to raise money to install a bronze bell that can be rung.

It's hard to see how such gimcrack trickery and throwback style are supposed to serve as the face of a museum devoted to our world-changing American Revolution. Our forefathers created a new nation by marrying what was good about the past with the latest ideas about organizing society. The design for the Museum of the American Revolution should aspire to no less.

Contact Inga Saffron at 215-854-2213, or @ingasaffron.